Abstract: S[Objective] A field experiment was conducted to study the effect of foliar potassium application on the yield of late rice, K agronomy efficiency, K concentration in late rice plant, K uptake in rice plant, K use efficiency, yield components of late rice in potassium deficient paddy field in order to provide guidance for rice production in potassium deficient paddy field in the south. [Method]KH2PO4, KCl and KNO3 were used as foliar potassium. There were 13 treatments included. The yields of rice and straw were estimated. The nitrogen, phosphorus and potassium content of rice and straw were analyzed and tested. The N, P, and K absorption of rice plant were calculated. [Result]It was showed that, foliar spray of KCl; the mixture of KH2PO4 and KNO3; the mixture of KH2PO4, KCl, KNO3, urea and pest control drugs all increased the yield of late rice in potassium deficient paddy field. Foliar Spray of KCl got the best result in increasing the yield. Foliar potassium application in the active tillering stage got the best result, and secondly in the initial heading stage. Foliar Spray of the mixture of KH2PO4 and KNO3; the mixture of KH2PO4 and KCl; the mixture of KH2PO4, KNO3, KCl, urea and pest control drugs all help improve the potash absorption and utilization of late rice. Foliar application of potassium fertilizer has greater impact on the potassium content of rice straw. [Conclusion]As the late rice grows in the potassium deficient paddy field, foliar potassium application was only a supplement, which can not replace the root fertilization.