Abstract: An incubation experiment was carried out for 42 days to study the effects of straw decomposition on Zn release from straw, the changes of Zn fractions and the content of soil microbial biomass Zn (Mic-Zn). The results show that the cumulative amount of CO2-C evolution and the content of soil microbial biomass C（Mic-C） are significantly increased with the increase of the straw amount, and these increases are affected by Zn concentration in straw and the inorganic Zn application. Moreover, whether the straw is added in soil or not, the contents of soil Mic-Zn, DTPA-Zn, exchangeable Zn (Ex-Zn) and loosely organic bound Zn (Wbo-Zn) are significantly increased when organic Zn fertilizer is added, and these four Zn fractions are also increased to some extent when high Zn concentration straw is added to soil compared to the low Zn concentration straw application. In conclusion, the addition of higher amount of straw as well as using straw with high Zn concentration can significantly increase the content of Wbo-Zn in soil, and increase the content of available Zn and soil Zn supplying capacity as well.