In view of students' individual difference in the learning process, in this paper we propose a personalized learning system, to which intelligent Agent technique and case-based reasoning mechanism are both applied, then we present a network learning environment based on mobile Agent and illustrate the environment's structure, working process, reasoning mechanism, major functions and implementation mechanism. Finally, the system is implemented on the mobile Agent platform Aglet. Keyword Personalized learning, Mobile Agent, Case-based Reasoning