Because the scale of software is getting larger and larger, a certain test coverage rate shall be got during software test and the quantities of generated test cases are great. In order to assign limited test resource reasonably, a case generation method for software test based on orthogonal experiment is proposed. Basic conceptions of orthogonal experiment are introduced. Incorporating with the characteristics of orthogonal method, applicability and operation process of orthogonal experiment in the area of design software test case are discussed. And an example is given finally. Experimental results show that fewer quantities of test cases are generated and good test effect is got.