In order to measure mission testability of complex repairable system reasonably, physical model and mathematical model of are constructed, considering function and mission character. Mission testability parameters are analyzed, and mission fault detection rate and mission fault isolation rate are chosen as metric parameter, then the physical model of mission testability is constructed, combining testability functional hierarchy. On this basis, hybrid series-wound/shunt-wound mathematical model of mission testability is constructed, and verification work is operated for fuel subsystem of submarine power system. The analytical result shows that the models constructed in this paper are close to physical truth, adaptive to the modeling of mission testability.