The 7–year field experiment was conducted to study the effects of applying different proportion of combination Astragalus sincus with chemical fertilizer on double rice yield, yield component, absorption of nitrogen and potassium and their apparent balance. Results showed that rational proportion of applying combined Astragalus sincus with chemical fertilizer could increase yield of both early and late rice. Compared to 100% CF treatment, the total yield from early and late rice was the highest in treatment with 20% GM, which increased by 8.3%, followed by the treatment with 40% GM, increased by 6.0%. The main reason for rice yield increase was derived from the increase of effective panicles per unit area, grain per panicle as well as plant height. Rational proportion of applying combined Astragalus sincus with chemical fertilizer could increase rice absorption for nitrogen and potassium. The accumulation of nitrogen and potassium whether in rice grain, rice straw or in the total rice plant in treatments of 20% GM and 40% GM were higher than that in treatment of 100% CF. Apparent nitrogen balance was surplus in treatments of 100% CF, 20% GM and 40% GM, whereas, apparent potassium balance was deficient in all the treatments, it was extreme deficient in treatment of 40% GM, followed by the treatment of 20% GM. Comprehensively taken the crop yield response, nutrient utilization as well as soil fertility cultivation into consideration, chemical fertilizer of nitrogen and potassium could be cut down 20%–40% by means of increase the application of Astragalus sincus.