As an excellent ATPG toll，TetraMAX ATPG enable to generate a test pattern set with high fault coverage in a short time. In this paper，by re-modeling the basic test pattern set generated by TetraMAX ATPG，a method for computing an optimal test pattern set based on minimum set covering problem is proposed. This method models the test pattern set reduction problem as an instance of set coverage problem. It can effectively reduce the scale of test set on the basis of guaranteeing the invariable fault coverage of test set，thereby reducing the test cost of the circuit testing. According to the stuck-at fault and the IDDQ Fault，the experimentd results show that the method has good reduction effect on both of them.