Test suite optimization aims at satisfying all testing objectives with the least number of test cases. According to the given testing objectives, the reduced testing requirement set can improve the effectiveness and efficiency of test suite optimization. This paper proposes a testing requirement reduction model that can describe the interrelations among the testing requirements in detail. Based on the model, this paper presents a testing requirement reduction method to generate the reduced testing requirement set, which is the basis of test suite generation, reduction and optimization. The experimental results show that the method is helpful to generate the smaller test suite and it contributes to the systematic, reasonable and effective testing.