Crop straw is rich in phosphorus (P), potassium (K) and other nutrient elements, but the optimal combined application of phosphorus and potassium on late japonica rice under crop residue incorporation is still unclear. A two-factor (P and K) experimental design was adopted in the field experiments, four levels of P and K fertilizer application rates were set up, which P₂O₅ were 0, 63.75, 127.50, 191.25 kg/hm² (denoted by P0, P1, P2, P3) and K₂O were 0, 102, 204, 306 kg/hm² (denoted by K0, K1, K2, K3), respectively. The yield, quality, and milled rice nitrogen accumulation of japonica rice were investigated and analyzed at rice harvest stage. Both P and K fertilizer could significantly enhance the yield, dry matter weight and harvest index of late japonica rice, and the significant interaction effect between them was found in our study. The reasonable combined application of P and K fertilizers had synergetic effect on the yield of late japonica rice, the high yield was achieved when the application rates of P and K fertilizer were 62.45 kg/hm²and 206.08 kg/hm², respectively. At the same time, the milled rice nitrogen accumulation was significantly increased by the reasonable combined application of P and K fertilizers. The brown rice rate, milled rice rate, head milled rice and gel consistency were improved by the reasonable combined application of P and K fertilizers, but the chalkiness rate, chalkiness degree, amylose content and protein content were also increased. Except that the peak viscosity, hot viscosity and cool viscosity had significant differences among the amount of K fertilizer, there were no significant differences in the rice RVA profile characteristics in P, K fertilizer and interaction of both. And the peak viscosity, hot viscosity and cool viscosity were first increased and then decreased with the increased amount of K fertilizer applied. In practices, optimizing the combined application of P and K fertilizers on japonica rice should be concerned during the late-rice cropping seasons in Southern China. The synergy effect of K and P was best under P1K2, which simultaneously achieved the high yield, high efficiency and high quality production of late japonica rice under upper-middle soil fertility and total rice straw incorporation.