Software testing is an important activity in the software development life cycle. and also expensive phase when compared to all other phases of the software development life cycle. Software testing purpose is to detect,software failures so that defects may be recoverd and corrected.Softwares are tested through test cases.A test case is a set of condition or variables variables under which a tester will determine whether an application or software system is working correctly or not.For many application test cases are generated automatically but the main problem is selecting a effective test cases among all test cases.The process of selecting a effective test cases from all test cases is called Test case selection.This process is used for finding a redundant test cases and removing the redundant test cases in a test suite is called test suite minimization. In this paper ,we propose a novel test suite reduction based on set theory.To demonstarate the applicability of this approach ,we conduct an experimental study ,The result shows that our technique is easy to implement and consumes less time