A long-term fertilization field experiment on rice has been going on since 1982 in the Red Soil Experiment Station of CAAS to investigate effects of combined application of organic and chemical fertilizers on crop yield and contents of soil available nitrogen, phosphorus and potassium. Results show that higher fertilization rate raised crop yield. Long-term application of organic and chemical fertilizer(NPKM) could increase the rice yield, and enrich the soil fertility. If long-term application chemical fertilizer(NPK), the rice production will reduce.In treatments the same in N application rate, amendment of phosphate fertilizer was higher than amendment of potash fertilizer, in yield-raising effect and it was particularly obvious with early rice. No significant difference was observed between treatments receiving for long organic fertilizer only and chemical fertilizer only in yield-raising effect. With the experiment going on and on, differences between treatments got more and more significant. In all the treatments, alkalysable-N increasing rates showed a similar trend, low-high-low. Organic fertilizer was better than chemical fertilizer in raising alkalysable-N content (p<0.05). Accumulation of soil available phosphorus was mainly related to application of chemical phosphate fertilizer. In terms of the mean content of soil available P of the years, the treatments displayed an order of NPKM, NPM and PKM > NPK > M and NKM (p<0.01). Soil available K increased the fastest in Treatments NPKM, NKM and PKM and the slowest in Treatment NPK. With increased N and P fertilizers application rate, surplus of nitrogen and phosphorus appeared in soil. However, Treatment NPKM was better than all the others in mitigating the surplus. Potassium deficit was observed in all the treatments, suggesting that to maintain the basic balance of soil potassium, at least 200 kg hm^-2 of K₂O should be supplemented in red soil paddy fields annually.