When optimizing the design of the step-up-stress accelerated degradation test based on Monte-Carlo, it is usually supposed that the product life follows the Weibull distribution.To solve the problem, an optimization design algorithm for acceleration degradation test under the premise of logarithmic normal distribution of life was studied.An optimized theoretical framework based on Monte-Carlo was given.Then, the statistical analysis model of step-up-stress degradation accelerated test for the photoelectric coupler was deduced.After the improvement to the existing Monte-Carlo simulation method, an improved Monte-Carlo simulation step-up-stress accelerated degradation test optimization design algorithm was proposed.Through the optimization design of a stepped acceleration degradation test for a certain photoelectric coupler, the effectiveness and feasibility of the improved Monte-Carlo simulation method proposed in this paper were verified.