Aiming at the present situation that the theory which guides the design and plan of reliability test type and stress level is insufficient, a reliability test design planning model based on potential defect exposure gain is proposed. Firstly, the environmental factors and test objectives of the reliability test are analyzed, and the potential defect exposure gain is defined. Then, the function model of the reliability test cost for each environmental factor and reliability improvement model is constructed from the perspective of the comprehensive degree and the severity of the reliability test, and a multi-objective nonlinear programming model is built with the test cost constraints, whose targets are both maximization of the potential defect exposure gain and the reliability improvement, and the solution method of the model is given. Finally, an example of the Harbinger system is given to obtain the optimal test scheme which satisfies the constraints and verifies the validity and feasibility of the proposed method.