The invention provides a detection algorithm for grid line offset on the surface of a cell. The detection algorithm includes the steps of performing preprocessing of image correction and image conversion on each frame of acquired image to obtain a target image of a photovoltaic cell; carrying out threshold segmentation of the target image, filling a grid line part, then carrying out shape conversion to eliminate the influence of defects at welding spots of the cell on the outline extraction, and accurately extracting the outline 1 of the edge of the cell; processing the target image by using grayscale top-hat transform to obtain a cell image only containing the grid line part; enhancing the image to eliminate the influence of a discontinuous grid line caused by the welding spots; carryingout threshold segmentation, and filling a gate line part to extract the outline 2 of the outermost peripheral gate line of the cell; and calculating the minimum distance between the outline 1 of the edge and the outline 2 of the outermost peripheral gate line of the cell, setting a threshold and comparing the minimum distance with the threshold to realize the detection of the grid line offset on the surface of the photovoltaic cell.