To reduce the time and cost of durability and reliability tests that are crucial tasks in the development process of a vehicle, accelerated life testing (ALT) that applies high-stress conditions in a short period should be performed [1]. As a vehicle becomes electrification and compact, the electric traction motor and inverter system of an electric vehicle (EV) are integrated, so the electric traction motor and inverter system must be tested simultaneously. This paper proposes a method for design of ALT cycle to develop an optimum ALT that simultaneously assesses the mechanical damage to the electric traction motor and the electrical damage to the inverter system. Factors for the acceleration of life of the system during driving and regenerative braking are investigated and simulation models of EV to predict the responses such as design targets and evaluation conditions need to be constructed. However, the development of accelerated life testing of EV systems has not been systematically analyzed but has been developed based on the long-term knowledge and experience of expert engineers. To achieve the optimum ALT cycle, the following five techniques are required. First, simple driving scenarios for the ALT are extracted by analyzing the driving conditions of various field tests through accurate measurement of motor torques and motor speeds. Second, a methodology for EV modeling and lifespan prediction of the electric traction motor and inverter system based on analytical mechanics is given. Third, discrete scenario variables corresponding to the simple driving scenarios are defined. Fourth, a new optimization problem for ALT cycle is formulated to generate an optimum ALT cycle. The test requirements of an ALT are reflected in the constraints of the optimization formulation. Finally, the defined optimization problem is solved using appropriate algorithms. The proposed methods applies to the ALT cycles for a middle class EV. Using GA in MATLAB, the optimum ALT cycles satisfying the test requirements for designing an electric traction motor and inverter system are obtained efficiently. Therefore, the optimization method may promise that the vehicle development period can be dramatically shorten while enhancing the quality of the ALT of EVs.