A key factor of reducing software development cost is how to improve the reliability and consistency of large and complicated software. Many CASE tools have emerged. This paper presents a large CASE tool called CPSL / CPSA (Chinese Problem Statement Language/ Chinese Problem Statement Analyzer) which was developed as a Chinese version of PSL / PSA. The paper also describes an example of using CPSL / CPSA in a target application. CPSL/CPSA has been used successfully in the "Computer-aided Economics and In formation Management System”of Beijing Vegetable Corporation and the“Oil-depositionSimulation”of the Ministry of Petroleum of China.