To reduce the cultivation process of heavy plow,leakage phenomenon of tillage,improve work efficiency,a method of identifying path for rotary cultivator based on the paddy field unstructured environment color image collected by visual navigation system was designed.Choosing the suitable color feature of paddy field was discussed.Considering that the soil area has less noise and the straw area has more noise,the over and compensation method was used to denoise the paddy image.The feature value of each pixel color was acquired by progressively scanning the image.The border information was obtained by using difference of the color feature between the straw area and soil area.The least squares technique was used to make a line and acquire the elevation angle which is the steering angle of rotavator.The rotavator's direction of advance which is the path information was determined.This method achieved good results in static image processing.It will be improved by the field test.