To solve the problem that electroluminescence imaging cannot be performed due to the position deviation of photovoltaic (PV) modules, A machine vision inspection method for PV modules position deviation was studied. The edge features of the cell modules are obtained by image preprocessing, and the sub-pixel edge detection method is used to subdivide the edges to obtain the exact edge point coordinates. The subpixel edge points are then fitted using iterative reweighted least squares (IRLS) to obtain the equation of the edge lines. By comparing the fitting results with the basic least squares method, it is demonstrated that the algorithm is robust to outliers on the edges. The performance of the algorithm was then evaluated through position deviation detection experiments, and the results showed that the detection error of this algorithm is about 1.792%, and the average detection time is only 224.7ms, so it can meet the requirements of practical applications. Finally, a comparison experiment was conducted to verify the higher accuracy of the algorithm compared with the traditional method.