In recent years, with the vigorous promotion of straw returning to the field, rice and other crops have become less and less dependent on potassium fertilizer. On the basis of traditional compound fertilizer (he proportion of NPK is 15%, 15% and 15%), many large fertilizer enterprises have developed high-nitrogen and low-potassium compound fertilizer for rice and other crops. However, the application effect of high-nitrogen low-potassium compound fertilizers and their combination with potassium fertilizers on double-cropped rice is still unclear. This study conducted a field experiment under straw returning into the field, which included no potassium fertilizer (CK), high-nitrogen low-potassium compound fertilizers containing nitrogen, phosphorus, and potassium nutrients of 18%, 12%, and 10% (F), and F with potassium fertilizer (F+K) treatments. Then, the changes in yield, yield components, nitrogen, phosphorus, and potassium accumulation, and potassium fertilizer utilization rate of early and late rice under different treatments were analyzed. The results showed that compared with CK, the early rice yield of the F and F+K treatments were increased by 4.36% and 9.13%, respectively. The late rice yield were increased by 4.09% and 13.89%, respectively, and the total rice yield were increased by 4.22% and 11.65%, respectively. At the same time, the early and late rice yields of the F+K treatment were higher than those of the F treatment by 4.57% and 9.41%, respectively. The analysis of yield components showed that the F+K treatment mainly achieved rice yield improvement by increasing the number of spikes per plant in the early rice season, the number of spikes per plant and thousand grain weight in the late rice season. Because F+K treatment increased the potassium content of grain and straw, the accumulation of nitrogen and potassium in the early rice season under F+K treatment was higher than that under the CK treatment by 12.30% and 22.40%, respectively, while the accumulation of nitrogen, phosphorus, and potassium in the late rice season under F+K treatment were higher than that under the CK treatment by 11.89%, 21.62%, and 26.59%, respectively. The results of both seasons also showed that the accumulation of nitrogen, phosphorus, and potassium under F+K treatment was increased than that under the CK treatment by 12.07%, 22.45%, and 24.54%, respectively, and they were improved by 9.34%, 8.56%, and 11.28% higher than that under F treatment. Due to the large amount of potassium brought in by straw return, there was no significant differences for the potassium use efficiency between F+K and F treatments, but the variability of potassium fuse efficiency under F+K treatment was significantly reduced than F treatment. Therefore, it is recommended that high-nitrogen low-potassium type compound fertilizer be combined with potassium fertilizer in southern double-cropping rice areas to achieve the goal of rice yield and efficiency improvement under straw return conditions.