The health index is used to indicate the overall health status of the equipment, based on which a comprehensive evaluation model is constructed. A variable health factor is proposed to revise the health index of the equipment according to the aging formula of the power equipment health condition and multiple characteristic parameters of the equipment that reflect the operating state of the equipment. In order to comprehensively consider the importance of equipment characteristic parameters, the combination of the order relation method and the entropy weight method is utilized for the calculation method of the weight value of the feature parameter, which leads to more reasonable establishment of the comprehensive evaluation system of the equipment health condition. Finally, a nonlinear relation model based on time series analysis is developed to fit the trend comprehensive health index of the equipment, evaluate the future health status and predict the maintenance time node. This model is used to analyze the air compressor of an oxygen plant, and the results show that the model is effective and reasonable. This work is supported by National Natural Science Foundation of China (No. 61672032) and Science and Technology Project of Anhui Province (No. 1604a0702016).