Abstract: Currently,the rice planting area in Northeast China is significantly increasing,which are 6 times the area of the early era of reform and opening-up.Rice straw returning to soil is a routine agricultural practice in Heilongjiang Land Reclamation Bureau,which can enhance the straw resource utilization and reduce environmental pollution.Here,we conducted a seven-year field experiment with combined application of straw-decomposing inoculants and returning straw in Heilongjiang 850 Farm,their effects on soil physical and chemical properties and rice yields were investigated.The field without returning straw used as a control (CK).Then,we analyzed the contents and changes of soil bulk densities,organic matter,available phosphorus,slowly-available and readily available potassium,pH and CEC (Cation Exchange Capacity) values and the rice yield.The results showed that the average rice yield with straw returning was significantly higher than that with CK.After 7 years,the contents of soil organic matter and pH with straw returning treatment did not significantly change; soil bulk density significantly decreased by 0.07 g·cm^-3 compared to CK; the contents of soil available phosphorus,slowly-available and readily available potassium,and CEC values significantly increased by 11.2%,14.3%,42.3% and 7.0%,respectively.Compared with CK,the contents of soil available phosphorus,slowly-available and readily available potassium,and CEC values with straw returning treatment significantly increased by 10.4%,14.1%,45.0% and 6.3%,respectively.In conclusion,long-term rice straw returning with straw-decomposing inoculants could improve soil physical and chemical properties and increase the rice yield,and the trend would be increasing with straw return times.