wherein PG₂, PG₆, PG₈, PG₉, PG₁₂, PG₁₃, PG₁₄, PG₁₅, PG₁₇, PG₁₈, PG₁₉, PG₂₂, PG₂₃, PG₂₅, PG₂₆, PG₂₈, PG₂₉, PG₃₀, PG₃₄, PG₃₅, PG₃₆, and PG₃₇ are independently hydrogen, benzyl, 2-naphthylmethyl tert-butyldimethylsilyl, tert-butyldiphenylsilyl or triethylsilyl;

PG₁ is any of hydrogen, methyl, ethyl, tert-butyl, or benzyl;

PG₄ and PG₅ form propylidene;

PG₇, PG₁₁, PG₁₆, PG₂₁, PG₂₇, PG₃₂, PG₃₃, and R₃₈ are selected from the group consisting of acetyl, chloroacetyl, benzoyl, pivaloyl, acetylpropionyl, 9-pentamethoxycarbonyl, 2-naphthylmethyl, and 2-p-methoxybenzyl;

PG₁₀ is one of acetyl, chloroacetyl, benzoyl, pivaloyl, acetylpropionyl, or 9-pentamethoxycarbonyl;

PG₂₀ is monochloroacetyl; PG₂₄ is benzyl; PG₃₁ is benzyl;

a Linker is —(CH₂)_n—N—Y₁Y₂ or —(CH₂)_n—S—Y₁, wherein n=1-10, and Y₁ and Y₂ are independently hydrogen, benzyl, 2-naphthylmethyl, or benzylmethoxycarbonyl; and

LG is a leaving group, and is selected from any of halogen, trichloroacetimidate, N-phenyltrifluoroacetimidate glycoside, methylthio, ethylthio, phenylthio, p-tolylthio, and dibenzyl phosphate;

the method comprising the following steps:

(a) performing a glycosylation reaction between a saccharide block donor formula 3 and a saccharide block receptor formula 2 to prepare a disaccharide compound 11 by the following synthesis route:

(b) removing the PG₇ protecting group of the disaccharide 11 selectively to prepare disaccharide 12; and performing a glycosylation reaction between the disaccharide 12 and a saccharide block donor formula 4 in the presence of an accelerator to prepare a trisaccharide compound 13 by the following synthesis route:

(c) removing the PG₁₁ protecting group of the trisaccharide compound 13 selectively to prepare trisaccharide 14; and performing a glycosylation reaction between the trisaccharide 14 and a saccharide block donor formula 5 in the presence of an accelerator to prepare a tetrasaccharide compound 15 by the following synthesis route:

(d) removing the PG₁₆ protecting group of the tetrasaccharide 15 selectively to prepare tetrasaccharide 16; and performing a glycosylation reaction between the tetrasaccharide 16 and a saccharide block donor formula 6 in the presence of an accelerator to prepare a pentasaccharide compound 17 by the following synthesis route:

(e) performing a glycosylation reaction between a saccharide block donor formula 7 and a saccharide block receptor formula 9 under the catalysis of an accelerator to prepare disaccharide 18; and removing PG₂₉ of the disaccharide 18 selectively to prepare disaccharide 19 and further performing a glycosylation reaction between the disaccharide 19 and a saccharide block donor formula 7 under the catalysis of an accelerator to prepare a trisaccharide module 20; and after R₃₈ is removed, performing a reaction of the terminal hydroxyl with trichloroacetonitrile or phenyltrifluoroacetyl chloride under an alkaline catalyst to prepare a trisaccharide donor 21 by the following synthesis route:

(f) removing the PG₂₁ protecting group of the pentasaccharide compound 17 selectively to prepare pentasaccharide 22; and performing a glycosylation reaction between the pentasaccharide 22 and a trisaccharide donor 21 in the presence of an accelerator to prepare an octasaccharide compound 23 by the following synthesis route:

(g) performing a glycosylation reaction between a glycosyl donor formula 7 and a receptor formula 24 under the catalysis of an accelerator to prepare disaccharide 25; and removing R₃₈ of the disaccharide 25 selectively, and performing a reaction of the terminal hydroxyl with trichloroacetonitrile or phenyltrifluoroacetyl chloride under an alkaline catalyst to prepare a disaccharide receptor 26 by the following synthesis route:

(h) removing the PG₂₀ protecting group of the octasaccharide 23 selectively to prepare octasaccharide 27; performing a glycosylation reaction between the octasaccharide 27 and a monosaccharide donor formula 8 under an accelerator to prepare a nonasaccharide compound 28; and removing the protecting group PG₃₂ of the nonasaccharide 28 selectively to prepare a nonasaccharide receptor 29, and performing a glycosylation reaction between the nonasaccharide receptor 29 and a glycosyl donor 26 under an accelerator to prepare undecasaccharide 30 by the following synthesis route:

(i) removing an acyl protecting group of the undecasaccharide 30 under an alkaline conditions and an aromatic protecting of the undecasaccharide group under a palladium on carbon/hydrogen condition to complete deprotection, resulting in a completely deprotected H. pylori lipopolysaccharide core undecasaccharide antigen as shown in formula 1.