Separating technology is very important for the spacecraft exploring the deep space, and the attitude of separated spacecraft suffers from the design parameters of separating mechanism, the results of which make the motion performance index uncertain. Based on the dynamic model, the parameters sensibility analysis, separating safe distance analysis, parameter random test analysis, and multi?parameters combination limit case analysis are computed, the result of which is estimated on how the deviation of parameters affects the spacecraft attitude. The analytical method and results have resolved the difficult technology of spacecraft separation suffer from the influence of multi?parameters deviation, on which the reference is provided about high precision and high reliability separating design.