An image algorithm to detect the navigation route and the filed end while the cotton plastic film mulch planter was working in the field was studied. The method of Daubechies wavelet transform was used to smooth and filter the image of the cotton sowing operation under the natural environment. The trough of the vertical cumulative histogram in the image processing region was detected in the first frame image. Based on this, the candidate points were detected scanning from the bottom row of the image to the top by using the method of detecting the trough of the local window cumulative histogram. For other frame images, the candidate points were detected segment by segment by the association between the navigation route of the current frame and that of the previous frame. Then the navigation route was fitted based on the passing a known point Hough transform (PKPHT). The experiments showed that the algorithm could quickly and accurately detect the navigation route and the field end while the cotton plastic film mulch sowing work. The average processing time of each frame was 72.02ms, which could meet the actual sowing work requirement of the film mulch planter.