A method for visual simulating leaf color based on the relative content of chlorophyll was proposed. The mathematical model between cucumber leaf color components and chlorophyll relative content was established according to images acquisited from real field and measuring chlorophyll relative content (SPAD) of the cucumber leaf in normal growth state continuously, and the model was also verified by using root-mean-square error (RMSE). The results showed that the RMSE between the observed values (R, G, B) and simulated vales(R, G, B) in leaf are 13.43%, 8.47%, 7.42% respectively. The rendering for the spatial distribution of apparent color of cucumber leaf was realized by combining with a black and white pigment distribution texture which was a grayscale image before being preprocessed. Then the high level shader language (OpenGL 2.0 Shader Language) was used to realize the rendering of apparent color changing process of cucumber leaf. The above process showed that the method proposed can achieve better realistic rendering results.