[Purpose] Controlled release potassium chloride can achieve slow release of potassium ions synchronized with crop absorption, while ensuring the effectiveness of potassium ions in the soil, meeting the potassium demand of crops in the later stages of growth, and significantly improving potassium fertilizer utilization efficiency. Exploring the effects of long-term application of controlled release potassium chloride and its mixed fertilizers on maize yield and quality, providing technical support for achieving high-quality maize production. [Method] A field long-term positioning experiment based on the application of controlled release potassium chloride to summer maize (Zea mays L., Zhengdan 958) was conducted (starting from 2014). Six treatments were set up, including no potassium fertilizer (CK), constant ordinary potassium chloride (K), controlled-release potassium chloride (CRK1), reduced potassium amount by 1/3 polyurethane coated potassium chloride (CRK2), constant mixed potassium chloride (BBF1), and reduced potassium amount by 1/3 mixed potassium chloride (BBF2). Relevant indicators such as maize growth, soil potassium supply level, potassium absorption capacity, and photosynthesis were calibrated during the tasseling period, and corn quality and agronomic benefits were measured during the mature period. Measurement. [Results] (1) The corn yield, aboveground biomass, and economic benefits of BBF1 treatment were the highest, at 12157 kg/hm2, 19954 kg/hm2, and 19183 yuan/hm2, respectively. Under equal potassium conditions, compared with other potassium application treatments, they significantly increased by 5.68% to 16.06%, 1.11% to 10.44%, and 10.39% to 28.37%, respectively. Compared with BBF1 treatment, BBF2 significantly increased potassium fertilizer utilization by 9.44%. (2) The potassium ion content in CRK1 and BBF1 was significantly increased by 19.93% and 13.89% compared to K, and significantly increased by 16.05% and 19.03% compared to CRK2 and BBF2, respectively. After reducing by one-third, CRK2 and BBF2 were not significantly higher than K. CRK1 significantly increased SPAD value by 7.32%, LAI value by 7.04%, and net photosynthetic rate by 18.58% compared to K. After reducing by one-third, CRK2 was not significantly higher than CRK1 and K. (3) Compared with K treatment, CRK1 treatment increased the crude protein, starch, and oil content of corn kernels by 4.23%, 4.46%, and 5.65%, respectively; After reducing potassium by one-third, CRK2 still increased the crude protein, starch, and oil content of corn kernels compared to K treatment. The mixed application of controlled release potassium chloride and ordinary potassium chloride (BBF1) further increased the crude protein, starch, and oil content per unit area of corn kernels compared to K treatment, but the difference was not significant compared to CRK1 treatment; After reducing potassium by one-third, there was no significant difference in starch and oil content per unit area of corn kernels between BBF2 treatment and CRK1 and BBF1 treatment. [Conclusion] Controlled release potassium chloride can meet the potassium requirements for maize growth and quality formation, improve maize growth, optimize the quality traits of maize grains, significantly increase maize yield and potassium fertilizer utilization efficiency, reduce fertilizer input costs, and achieve the goal of reducing yield without reducing yield and quality.