Abstract: Based on the analyses of the structure characteristics, running and hydrogological conditions of the uranium mill-tailing site in southern China, the geologicaland hydrogeological conditions were summarized. Then the one-dimension coupled solute reaction-transport numerical model was employed to simulate the U(Ⅵ) migration in shallow groundwater at the site studied here using PHREEQC-Ⅱ code. The U(Ⅵ) concentration distribution as a function of time and distance was calculated and analysed with various diffusing coefficients and dispersion coefficients. The results show that PHREEQC-Ⅱ code can successfully simulate the U(Ⅵ) migration in shallow groundwater of site studied here. The effect of dispersion on the U(Ⅵ) migration in shallow groundwater is significant, while the molecule diffusion can be ignored in this model. Therefore, the dispersion coefficient is a key parameter in this modelling.