In order to explore the changes of soil nitrogen, phosphorus and potassium contents and nutrient balance after applying biogas slurry in alluvial paddy soil in Chengdu Plain, and realize the green development of biogas slurry resource utilization. Field experiments were conducted. Ten gradients of biogas slurry application rate were set up, and clear water and conventional fertilizers were taken as control. The effects of different amounts of biogas slurry on soil nitrogen, phosphorus, potassium and other nutrients contents were studied, and the balance of nutrients in the field was comprehensively analyzed. The results showed that the contents of total nitrogen, alkali-hydrolyzed nitrogen, total potassium and available potassium were higher when the biogas slurry application rate was 108.0~126.0 t/hm², which were 1.35~1.42 g/kg, 63.31~65.34 mg/kg, 12.90~13.26 g/kg and 45.45~59.25 mg/kg. With the increasing of biogas slurry application, the total phosphorus content of soil (0.92~1.10 g/kg) did not change significantly, while the available phosphorus content (8.49~18.85 mg/kg) decreased by 11.0%~59.9% compared with the clear water control. The balance of nitrogen, phosphorus and potassium in the biogas slurry treatment groups were -25.61~66.68, -7.99~-15.34 and -81.33~-145.82 kg/hm². When the amount of biogas slurry was more than 108.0 t/hm², the nitrogen balance was basically maintained. With increasing of biogas slurry application, phosphorus deficit was alleviated, while the potassium deficit was aggravated. Applying appropriate amount of biogas slurry could increase the contents of nitrogen and potassium in soil, but it was difficult to meet the balance of phosphorus and potassium in soil by applying biogas slurry alone. Therefore, the application rate of biogas slurry should be controlled in the range of 108.0~144.0 t/hm² in the actual production, and combined with 10~15 kg/hm² phosphate fertilizer and 115~120 kg/hm² potassium fertilizer to achieve the desired effect.