Abstract: The study and application of leaf colour identifying technology using computer vision is one of the most important branches in the field of agricultural information technology. In order to apply it to virtual crop better, RGB system was introduced to identify wheat leaf colour. By using the light treatment technology in virtual reality technology, the sunlight was divided into three parts as environment light, diffusion light and lens light, and the effects of these three parts of light on leaf colour were simulated. According to the intrinsic relationship between colour and the sunlight, the model for identifying the wheat leaf colour was developed. This model is characterized with high accuracy and strong predicability, according to the verification.