Abstract: Operation along crop row is a basic function of vision navigation for agricultural robot. The complex external factors of working environment in the field, such as existed shadow and weather change etc., make the navigation parameters extracting become more difficult. Aiming at shadow influence problem in vision navigation process of agricultural robot, illumination invariant image based on shadow removal algorithm was introduced. An enhanced OSTU image segmentation method was used, and an optimized Hough transformation algorithm was used to extract crop line, and coordinate transform was applied to obtain navigation parameters. Finally, tests of following crop row showed that shadow removal method based on illumination invariant image satisfied real-time requirement of system and improved the robustness of extracting navigation parameters under variable daylight illuminants.