Based on a 26-year-long fertilization experiment on a paddy field in the Taihu Lake Region，effects of long-term fertilization on profile distribution of soil nitrogen and C/N ratio，soil nitrogen mineralization characteristics under 10 ℃ and 30 ℃，and relationship between cumulative mineralization and effective accumulated temperature were studied. Results show: (1) Nitrogen accumulation significantly increased in the topsoil (0～20 cm)，where total nitrogen was higher in Treatments MNP (manure and fertilizer N，P)，MNPK (manure and fertilizer N，P，K)，MRN (Manure，rice straw and fertilizer N) and M0 (only manure application) than in Treatments CNP (chemical fertilizer N and P)，CNPK (Chemical fertilizer N，P and K) and CK (no fertilizer application)，however，in the 20～30 cm soil layer，it was just the contrary. And in the 40～50 cm soil layer，little difference was observed between the two groups; (2) Organic manure and straw applications may result in decrease in C/N ratio in the topsoil，where the ratio displayed an order of CNPK>MNPK，CK>M0，and was the lowest in MRN，while in the 20～50 cm soil layer，the ratio was were general higher in the organic manure treatments than in the chemical fertilizer treatments. And the subsoil in the chemical fertilizer treatments were higher soil organic matter decomposition degree; (3) Under 30℃ soil mineralization leveled off pretty quickly，but with high cumulative mineralization，while under 10℃，soil mineralization rate in the late incubation period was higher than under 30℃，but the cumulative mineralization was relatively lower. Obviously low temperature led to in decrease in soil mineralization rate. The relationship between cumulative mineralization and effective accumulated temperature well fit the effective accumulated temperature model (EATM) (p<0.01)，its mineralization constant K reflected similar mineralization potentials of the various treatments at the initial stage of mineralization. Difference between treatments in mineralization constant n reflected higher mineralization potentials in Treatments MRN，MNP，CNPK，and CNP in the late stage.