Considering to the problems of long test timehigh cost and low efficiency for the double-step-down-stress degradation test for high-reliabilitylong-life productswe presented an optimal design method based on Monte-Carlo simulation for double-step-down-stress accelerated degradation test(DSDS-ADT).Simulation was made for the acceleration test with Monte-Carlo method.Taking the number of inspections on each unitthe number of test units and inspection frequency as variablesand the total experimental cost as a constraintthe asymptotic variance estimation of 100 pth percentile of the lifetime distribution of the product as goal functionwe established the optimal designed model of DSDS-ADT based on Monte-Carlo simulation.Simulation results verify the feasibility and the validity of this methodand provided a theoretic support for optimal design of accelerated test in life prediction of electronic equipment.