This study aims to address the various challenges faced in university English writing instruction, such as large class sizes, insufficient personalized guidance, and limited teaching time. The paper provides a detailed account of the design, implementation, and evaluation of an AI-driven adaptive learning system. This system utilizes a microservices architecture and integrates advanced AI technologies, including natural language processing, reinforcement learning, and personalized recommendation algorithms. Core functionalities such as automatic writing assessment and personalized learning path recommendations have been implemented. Through comprehensive testing and evaluation, the system has met its expected goals in terms of functionality, performance, usability, and security. The results indicate that the system significantly improves writing assessment efficiency and accuracy, enhances learning outcomes, and has received high user satisfaction. This research offers an innovative solution to improve university English writing instruction.