The variations in testing requirements often result in the problem of numerous test cases and low efficiency in regression testing. To solve this problem, a reduction method of testing requirements is proposed based on the relation mode in this paper. This method analyzes the relationship between the modules and testing requirements, then determines the varied regression testing requirements, and gets the final testing requirement set by reduction of the varied regression testing requirement set and the original testing requirement set in three times. If test cases are generated and reduced on the basis of the testing requirement reduction set, the efficiency of the regression testing will be improved.