Abstract: Computerized adaptive test (CAT) system is an intelligence test system based on Item Response Theory (IRT).It can not only improve test efficiency but also enhance the accuracy of ability evaluation to tester.This article describes the details of IRT,discusses the operational principle and implementation process of CAT as well as the correlative knowledge of system design,proposed a solution to the estimation of initial ability value and optimized the termination conditions of the test.Finally we provided an ideal test method for the personalized learning.