In the face of fierce competition, JLY supermarket is faced with the problem of improving service quality and customer satisfaction. Based on SERVQUAL model, this study investigated the service quality of supermarkets from the five dimensions of reliability, responsiveness, assurance, empathy, and tangibility. It found out the main factors affecting the service quality, and established the service quality improvement model. This survey adopted quantitative and qualitative methods, survey and focus group discussion as method implemented through snowball sampling using a network questionnaire survey platform. SPSS software was used for descriptive statistical analysis to analyze customers' perception and expectation of supermarket service and the gap between perceived service and expected service was brought out via mean value, standard deviation and weighted mean. The study found that the main factors affecting the service quality of JLY include employee salary, employee empowerment, employee training, resource support, service performance evaluation, service supervision and control, service demand and design, etc. Consequently, a supermarket service quality improvement model was proposed.