One of the most challenging work in non-photorealistic rendering research field is to studies of the simulation of Chinese ink wash drawing. By analyzing the Chinese ink wash drawing material and ink-wash diffusion mechanism, a new method based on genetic algorithm is presented to model the diffusion effect. The method first simulates the diffusion effect by binary gene encoding, initializing population and gene mutation. It constructs a list of mapping that describes the correspondence of Minkowski distance to the rate of gene mutation so that gene mutation can happen suitably by itself. As a result, modeling the diffusion of Chinese ink wash drawing can be finished automatically. All kinds of ink wash diffusion effects can be realized by some parameters, such as the scale of population, paper cell fiber threshold and so on; Furthermore, to improve the diffusion effect made by the simulation system above, the model uses Ashikhmin algorithm and Gaussian Distribution to simulate the characteristic of xuan-paper to make the diffusion effect with more fidelity. Experimental results demonstrate that this method simulates the typical effects of Chinese ink wash drawing successfully.