This study proposes a road crack image preprocessing method based on the fusion of a line segment detector (LSD) and fast line detector (FLD) to address the issue of linear interference, such as road signs and road edges, which affect road crack recognition. First, based on the LSD and FLD algorithms, line detection is performed on the crack image to obtain the line segment coordinate values of linear interferences. Second, by reconnecting the broken lines based on the line segment coordinate values returned by the line detection algorithm, the problem of extracting discontinuous line segments is solved using the line detection algorithm. Finally, the fast marching method (FMM) inpainting algorithm is used to eliminate linear interferences using the mask image of the linear interferences and the original image of the crack image obtained after reconnecting the line segments. Based on extensive experimental analysis, this method can effectively eliminate linear interference in crack images, improving the accuracy of crack detection by 7.1%.