Abstract: Lowering the false positive rate is a challenge for software testing based on defect patterns.This paper expands the typical interval computation and proposes a method for interval set computation.The proposed interval computation of various data types include real number variable,Boolean variable,pointer variable and array variable.May and Must set are used to compute interval restricted by conditional statement.Updated data flow equation is used to compute variables' interval in control flow traverse.The interval computation is used in software testing based on defect patterns.Experimental results show that it can reduce false positives and provide necessary information for defect testing.