injecting sulfur-containing flue gas into an injection well which is arranged in a well pattern of a sequestrated aquifer in advance, the formation water of the sequestrated aquifer being neutral or slightly alkaline, the injection pressure being smaller than or equal to a first preset pressure upper limit, and the well pattern being of a one-injection and one-production well pattern structure arranged in the sequestrated aquifer and forming one-dimensional linear flow or semi-one-dimensional linear flow;

transiting and injecting formation water into the formation at a first preset injection speed by an injection well of the well pattern after injecting the sulfur-containing flue gas for a first preset time, maintaining the first formation pressure, and conducting water drainage and gas production by a production well of the well pattern in a mode of a fixed bottom hole flowing pressure, the first preset pressure upper limit being 44.5 MPa;

and determining the well shut-in time according to the nitrogen molar concentration of the production well and conducting well shut-in;

wherein, the step of injecting sulfur-containing flue gas into an injection well which is arranged in a well pattern of a sequestrated aquifer in advance, comprises:

injecting sulfur-containing flue gas into an injection well which is arranged in a well pattern of a sequestrated aquifer in advance, and meanwhile conducting water drainage operation by a production well of the well pattern in a mode of a fixed bottom hole flowing pressure, the injection pressure being less than or equal to 44.5 MPa, and the duration of injecting the sulfur-containing flue gas being 58 days.