For meeting the requirement of complicated design restrictions, a set of performance indices was proposed, which was used to evaluate the efficiency of a space telescope secondary mirror adjusting mechanism. Based on these indices, a set of dimension parameters with high efficiency was obtained. By establishing the kinematic model, error model, statics model, dynamic model and analyzing the characters of these models, the Workspace Efficiency Index (WEI), Error Efficiency Index (EEI), Force Efficiency Index (FEI) and Energy Efficiency Index (EnEI) were proposed. The performance atlases method was used to investigate these indices. Four performance atlases of these indices were presented. Furthermore, a set of dimension parameters ((a, b, l)=(197 mm, 643 mm, 1 260 mm)) with high efficiency was obtained by optimizing these indices. The research result is helpful for engineering applications of this mechanism.