Abstract: In order to find out the proper proportions of crop straws and chemical fertilizer used in field, characteristic of nutrients release of rice straw, wheat straw and rapeseed straw were studied by method of nylon net bag under waterlogged incubation. The results showed that the decomposition rate of crop straws was much faster at the beginning stage and rapeseed straw decomposed faster than rice straw and wheat straw. And crop straws decomposition rate kept a slowly steady until the end of experiment, which had no obvious difference among three crop straws. After 124 days incubation, the cumulative decomposition rates of rice straw, wheat straw and rapeseed straw were 49.17%, 52.17% and 49.8%, respectively. The sequence of nutrients release rates of the three crop straws were K>P>C>N, while the sequence of nutrients release amount were C>K>N>P. C release rate of rice, wheat and rapeseed straw were up to 57.53, 66.58 and 52.54 percent, and N were up to 42.05, 49.26 and 57.83 percent, and P were up to 68.28, 59.93 and 67.32 percent after 124 days incubation, respectively. For all three crop straws K release rate was 98 percent within the first 12 days of incubation. It was indicated that on the basis of crop straws decomposition characteristics and nutrients release amount the application rates of K fertilizer should be decrease and used in crop growth later stage, while N and P should be maintained as usual practice at early crop growth stage.