In this paper, based on gas geochemical characteristic and geological background, the biogases in the Bohaiwan Basin are divided into two types of source rock-and hydrocarbon-derived biogases. The source rock-derived biogases are subdivided into primary and secondary biogases, and the hydrocarbon-derived biogas could be subdivided into anaerobic degradation biogas and aerobic degradation biogases. By mean of understanding the conditions of biogas source, reservoir, trap and preservation in the Bohaiwan basin, the authors consider that the Bohaiwan Basin have sufficient source of biogas, developed reservoir and suitable trap. The sealing capacity of cap rock, fault activity after Dongying movement is the key for biogas accumulation.