In recent years, the scale of cross-border e-commerce exports has been growing, and as an important foreign trading city in China, S City Post has landed the postal service function for cross-border e-commerce exports in cooperation with local customs and other public departments. With the rapid growth of business volume, the existing postal service faces challenges in terms of efficiency, quality and user satisfaction. In order to optimize service quality and enhance user satisfaction, this study designs the 3S model, which integrates the SERVQUAL model and the KANO model, and proposes an optimization strategy for cross-border e-commerce export postal service using GenAI-TRIZ, and the “Cross-border cloud access” service optimization scheme is designed. Based on 3S, the three design stages are service pain point identification, service demand analysis and service optimization proposal. In the first stage, the field observation method is focus on service pain points. In the second stage, the SERVQUAL and Kano Model are used to systematically classify and analyze the service needs, and four types of service needs are obtained. In the third stage, the service-oriented contradiction matrix is constructed by focusing on the needs that must be satisfied, the needs that should be considered as the focus of service optimization, and four optimization strategies are proposed based on the principle of TRIZ 40 innovations and inventions. Through this research, we expect to provide TRIZ and AI collaborative innovation new ideas and replicable technical paths for public service optimization, and provide reference for further development of cross-border e-commerce export postal service.