The performance requirements of pose and position fine tuning apparatus for secondary mirror in large optical telescope were analyzed.Based on Gough-Stewart manipulators,two design criteria for the optimal design of pose and position fine tuning apparatus were brought out,one is transmission precision performance and the other is stiffness performance.Two angular-dimensioned parameters and three nondimensionalized linear-dimensioned parameters as design parameters were selected to analyse the effect of each parameter on performances.Then,two global conditioning indexes were brought out,one is movement precision performance index and the other is stiffness performance index.Based on requirement for pose and position adjustments,a general workspace was adopted to replace the reachable workspace.In the guideline of unified objective method,a unified objective function and a mathematical model were established for solving a constrained single objective optimization problem,and an improved genetic algorithm was used to obtain the Pareto optimal solution within the definite areas selected.Experimental results indicate that the performance is optimal when the ratio of base radius to platform radius is 1.095.Compared with the optimal performance when the ratio of base radius to platform radius is less than 1,transmission precision performance index increases by 0.7% and stiffness performance index reduces by 4.0%.