5cm。In the farmland non-structurization natural environment, navigation route’s extraction algorithm was studied based on machine vision. The distance and angle between camera and navigation route was gained by the perspective projection. The algorithm was successfully transplanted to TMS320DM642 hardware platform, and optimized on a C programming language level. In the examination, it shows that the biggest error of deviation angle between camera and navigation route is 2° and the biggest deviation distance between camera and navigation route is 5cm.