Abstract: Taking a long-term fertilization experiment in Taoyuan Agro-ecosystem Research Station under Chinese Academy of Sciences as the platform, and selecting four treatments (no fertilization, CK; rice straw returning, C; nitrogen, phosphorus and potassium fertilization, NPK; and NPK+C) as the objects, soil samples were collected at the tillering, booting and maturing stages of rice, and the abundance, composition and diversity of nifHcontaining bacterial community were measured by realtime quantitative PCR and terminal restriction fragment length polymorphism (T-RFLP), aimed to understand the effects of rice straw returning on the nifHcontaining bacterial community in paddy soil.  Compared with CK, treatments NPK+C and NPK increased the abundance of nifHcontaining microorganisms significantly (except at tillering stage), and NPK+C had the highest abundance of nifHcontaining microorganisms. Under the effects of longterm fertilization, the composition of nifH gene community in CK differed obviously from that in the other three treatments. The nifH composition had definite difference between C and NPK, but less difference between NPK and NPK+C. Longterm fertilization did not induce significant changes in nifH diversity. Therefore, longterm rice straw returning not only induced the changes of nifH gene community composition, but also resulted in a significant increase in the abundance of nifHcontaining community, and hence, the increase of soil nitrogen fixing capacity.