The invention discloses an image detection method of farmland weak navigation information and a system thereof, relating to the field of machine vision navigation technology. The method comprises the following steps of: S1, collecting an image to be detected of current farmland; S2, judging whether the image to be detected is a first frame image, if so, carrying out navigation straight line detection of the first frame image, and returning to the step S1, otherwise, carrying out navigation line detection of a non first frame image; S3, carrying out farmland end detection according to a result of the navigation line detection of the non first frame image, judging whether reaches a farmland end or not, if so, ending the detection, and otherwise, returning to the step S1. According to the invention, by targeting a farmland work environment with weak navigation information, utilizing methods of wavelet transform and linear analysis, mutual association of front and rear frames, segmentation Hough transform and the like, in the condition that dividing lines of farmland areas are not obvious, the image identification of a navigation path is realized, and a detection result is accurate, stable and fast.