Testability indexes are the basis of testability design, validation and evaluation. To address the problems that the traditional testability indexes are mainly used to evaluate fault detectability level and fault isolability level, and are unable to describe testability level for equipment health management (EHM) comprehensively, based on the qualitative intrinsic requirements analysis of EHM on testability, five testability indexes were defined from the universe and instantaneous angles to describe the testability level for EHM quantitatively, and the detailed analysis and calculation process of the proposed indexes were presented based on failure mode state vector. A certain diesel engine body subsystem was introduced as a case example to illustrate the testability indexes calculation process, and application results show that the proposed indexes are feasible and rational, and they can guide the testability optimization design for EHM effectively.