Abstract: On the consideration of the shortage of common optimization design method for designing planetary gear accelerator in a loom of weft insertion with magnetic force, a reliability optimization design method taking gears’ stress and strength as random variables was proposed. Based on comprehensive consideration of loading capacity, compact structure, light-weight and transmission efficiency of planetary gear accelerator, its multi-objective reliability optimization design model was set up. In the model, the smallest volume and highest efficiency of the mechanism were taken as the objective functions while reliability conditions of planetary transmission and gears’ fatigue strength, the kinematic and geometric conditions of the planetary transmission were taken as constraints, then the goal programming and sequential quadratic programming algorithm in optimization toolbox of Matlab were used to solve the model. Compared with the common optimization design schemes, the volume of the planetary gear accelerator reduces by 19.42 percent while its efficiency is improved, which shows that the design method is practical, reliable and effective.