In order to solve the problems of multi-state impact on camera performance and to maximize efficiency， multi-states and their transition models were investigated. First， the origin of multi-state was identified， and the effect of deterioration of each function unit was analyzed. Then， a model containing multi-state transition was established. Finally， a simulation method is put forward. A brief case study indicated that considering multi-states would improve the accuracy and reliability of prediction， and that sensitivity analysis will help in balancing the system reliability requirement and system reliability. The multi-state reliability simulation method can be a more accurate method for predicting the reliability of space cameras and provides a practicable engineering solution.