step 1) drying and modifying a pretreated bamboo unit by using water vapor with a superheated temperature of 110-80° C., until a water content of the bamboo unit is 8-20%, to obtain a dried and modified bamboo unit; wherein the pretreating in step 1) specifically includes: removing an outer green part and an inner yellow part from the bamboo unit, steaming and softening, and then washing and grinding, to obtain the pretreated bamboo unit;

step 2) dipping the dried and modified bamboo unit in step 1) in a dopamine solution or spraying the dopamine solution thereon, and dried, to obtain a filamentous bamboo unit undergone polydopamine coating treatment;

step 3) dipping the filamentous bamboo unit undergone polydopamine coating treatment in step 2) in an adhesive I to perform adhesive dipping, draining, and drying, until the water content of the bamboo unit is 10%-16%, to obtain a blank;

step 4) curing and solidifying the blanks in step 3), to obtain a bamboo plate;

step 5) assembling and gluing two or more of the bamboo plates in step 4) according to a preset requirement, assembling the bamboo plates, and solidifying, to obtain a bamboo sleeper billet;

step 6) coating a dopamine solution on a surface of the bamboo sleeper billet in step 5), and then performing anti-mildew and/or anti-corrosion and/or anti-insect treatment, to obtain a bamboo sleeper undergone anti-mildew and/or anti-corrosion and/or anti-insect treatment; wherein the anti-mildew and/or anti-corrosion and/or anti-insect treatment in step 6) specifically includes: coating the dopamine solution on a surface of the bamboo sleeper billet and drying, coating a titanyl sulfate solution, drying, and then coating a silver nitrate solution, and drying, to obtain the bamboo sleeper; and

step 7) locking and fastening the bamboo sleepers undergone anti-mildew and/or anti-corrosion and/or anti-insect treatment in step 6) by using a fastener, to obtain the assembled bamboo sleeper.