Abstract: According to the shortcoming of Pairwise testing，which needs abundant test case set，an engineering approach for the generation of optimization test case set based on factor relationship（FRBT） is put forward.By analyzing the UML design model and resource code according to the Factor Relationship Calculation Model to work out the matrix of factor relationship，and make the form which covers each pair of input parameters by the way of one to one orthogonality through using the algorithm of generation covering form based on factor relationship.The most important improvement point is using math model to choose the covering factors，as a result，reducing the risk and unsteadiness caused by other engineering approach which chooses covering factor only depending on STE（Software Test Engineer），so making the test design more quick and objective.The experiment results demonstrate that FRBT not only generates the minimum test cases，but also improves the rate of discovering defect from 26.518% to 52.568%.