The invention discloses a membrane separation biogas biological desulfurization method and device. The method comprises separating hydrogen sulfide gas and biogas by a hollow fiber membrane assembly, carrying out biological desulfurization treatment on the separated hydrogen sulfide gas in a filling material in a tower outside the hollow fiber membrane assembly, and collecting the biogas separated from hydrogen sulfide by the hollow fiber membrane assembly. The method and device solve the problem that a biogas reaction tower biological desulfurization technology utilizes air to dilute biogas, an absorption liquid is treated difficultly, residual oxygen in the bio-desulfurated biogas is produced by an aeration reaction tower outside biogas and low concentration hydrogen sulfide biogas biological treatment efficiency is low, realizes high efficiency and stable removal of hydrogen sulfide in biogas, realizes recovery of elemental sulfur form and reduces an operation cost.