In the rice-wheat production areas of the Yangtze River's middle and lower reaches, soil potassium availability is relatively low, making it one of the typical limiting factors for improving crop yields and nutrient efficiency. From 2020 to 2022, a field experiment on nitrogen-potassium interactions (with 4 nitrogen and 3 potassium application levels) was conducted in Jiangyan City, Jiangsu Province, to study the synergistic effect of nitrogen and potassium on wheat yield. Using the latest nitrogen balance model, the study also quantified the impact of nitrogen-potassium synergy on field wheat’s active nitrogen emissions. The results showed that, without nitrogen fertilizer, the application of potassium fertilizer did not significantly improve wheat yield. When nitrogen fertilizer was applied at the optimal level (180kg/hm2), the K100 treatment increased wheat yield by 48% and improved total nitrogen absorption in the aboveground part by 52%, compared to no potassium application. Compared to the traditional farmer practice of N270K50, the N180K100 combination reduced apparent nitrogen surplus by 76% and active nitrogen emissions by 43%. Strengthening nitrogen-potassium synergy management in the potassium-deficient rice-wheat regions of the Yangtze River Delta is of great significance for achieving sustainable and intensive wheat production and promoting green agriculture.