Abstract: Condition-based maintenance (CBM), which is triggered by equipment health evaluation results, has become a new support mode of complex equipment. Aiming at the problem that uncertain health evaluation has certainly an impact on CBM behavior, and further on equipment operational readiness, three quantitative indexes, including accurate evaluation probability, excessive evaluation probability and deficient evaluation probability, were firstly defined to describe the uncertainty of health evaluation, and the steady-state availability was applied to describe CBM effect. Then the discrete state Markov process and the steady-state balance theory were used to construct the dependency among steady-state availability and accurate evaluation probability and excessive evaluation probability，which provides the base for further study of health evaluation theory. Finally, two cases were used to validate and verify the proposed method. The results show that the proposed method is feasible and effective.

Key words: methodology of system engineering, uncertain health evaluation, condition-based maintenance, quantitative index, steady-state availability