Abstract: A field experiment was conducted to study the effects of organic fertilizer application on yield, nitrogen fertilizer utilization and soil fertility of the mid-season rice - ratooning rice to provide technical and theoretical support for high yield and high economic return of mid-season rice - ratooning rice in paddy field. Two rice cultivars, Zhunliangyou 608 (ZLY 608, 2018) and Jingliang-youhuazhan (JLYHZ, 2019) were selected and four treatments were set as follows: planting azolla (OM₁), planting green manure and straw return (OM₂), pig manure application with 15% chemical fertilizer reduction (OM₃) and chemical fertilizer application (CK). Rice yield, yield components, nitrogen utilization and soil fertility were examined. Compared with CK, organic fertilizer application significantly increased the yield of mid-season rice - ratooning rice by 12.0% ~ 25.0% and 16.7% ~ 26.3% in main season and ratooning season, respectively (P < 0.05). Organic fertilizer application significantly increased the number of grains per panicle in the main season and productive panicle in the two seasons (P < 0.05). Organic fertilizer application significantly increased the dry matter accumulation at each stage by 27.0% ~ 83.3% (P < 0.05). Organic fertilizer application significantly increased the nitrogen partial factor productivity (NPFP) by 41.1% in the main season and 33.0% in the ratoon season in OM₃ (P < 0.05). However, the nitrogen use efficiency (NUE) of mid-season rice - ratooning rice was decreased by 21.4% ~ 32.9%, 13.2% ~ 22.7% in the main season and ratoon season, respectively (P < 0.05). To some extent, organic fertilizer application significantly improved the soil fertility in the mid-season rice - ratooning rice system (P < 0.05). Compared with CK, OM₁ significantly increased the alkaline nitrogen content, OM₂ significantly increased the available phosphorus, available potassium, organic matter and total potassium, OM₃ significantly increased the alkaline nitrogen, available phosphorus, organic matter and total phosphorus (P < 0.05). In conclusion, organic fertilization significantly improves the yield, nitrogen utilization and soil fertility in mid-season rice - ratooning rice system, and the performance of the three modes is in the order of OM₃ > OM₂ > OM₁.