This paper introduces an English online learning system based on Web technology, and describes the system design schema in detail and the related key technologies. First of all, intelligent test paper generation algorithm and strategies of the system are analyzed, combining practicality and operability of proposed algorithm with practical technical indicators the mathematical model is established, and an improved genetic algorithm is designed for solving the model, a group of test papers are generated randomly by test paper indicators to meet the individual needs of different users. Secondly, by introducing Ajax technology, it realizes the time controll of examinations, resolve the bottlenecks problem which is caused by B/S structure, and ease the flow of data.