Abstract: Aiming at photovoltaic power plants with complex installation conditions, this paper proposed a method based on the comparison of working conditions between photovoltaic modules to achieve fault detection. First, to consider accuracy and simplicity, an analytical and linear model of module output was introduced. Moreover, a characteristic value was proposed, together with its extracting, calculation and probability analysis method. On this basis, a fault detection method for modules in PV stations, especially with complex installation conditions, was designed. Finally, the effectiveness of this method was verified by simulation. Specially, the influence of solving characteristic value based on linear model on the accuracy of fault detection was discussed, and a method to improve the accuracy of the fault judgment of this method was proposed.