Abstract: In order to diagnose the health status of the photovoltaic modules, a method of quantitative detection for the health checking of the photovoltaic modules is proposed based on three indexes of the photogenerating current, the equivalent series resistance and the equivalent parallel resistance. Firstly, the improved cuckoo algorithm was used to identify the parameters of the measured I-U curve of the photovoltaic modules, forming the measured health curve. Then, the theoretical health curve was determined by the natural aging model of the photovoltaic modules. Next, the offset between the measured health curve and the theoretical health curve was calculated and the numerical correction was carried out with the grey correlation analysis. The health degree H parameter is defined to calculate the quantified value of the health status of the photovoltaic modules. Simulation analysis and experimental test show that this method is able to diagnose the health degree of the PV module effectively in different environments, providing a reference for the PV module maintenance.