In the quality condition assessment of equipment, a diamond frame model of the index system is put forward in order to shorten the time for the condition assessment aiming at missions while improving the quality management efficiency, combat preparation efficiency, and the level of combat readiness. Then, the characteristics of index convergence methods are analyzed. After that, the index optimization model is built and the quality condition is preliminarily assessed based on Principal Component Analysis ( PCA). Finally, a numerical example is given to verify the feasibility of the method. The analysis shows that: PCA has strong superiority in original index feature transformation and incremental index processing, which can improve the evaluation efficiency, and achieve optimized distinguishing of the state assessment indexes between normal state and state of combat preparation .