Abstract: In order to study the influence of uranium chemical fraction on the in-situ leaching mining, the uranium chemical fractions of different samples from the same mining area of a sandstone uranium mine in Xinjiang were separated by step-by-step extraction method, and the uranium grades were determined. Combined with indoor leaching experiment and on-site monitoring experiment, the relationship between uranium chemical fraction and leaching kinetic as well as leaching process was explored. The results show that there are differences in the chemical fractions of uranium deposits in different sections of the same mining area. The leaching kinetics of uranium is affected by four fractions (F1-F4) in the form of internal diffusion controlling firstly and then chemical reaction. Moreover, the apparent rate constant of uranium leaching increases with the percentage of F1-F4. The uranium concentrations in the pregnant solutions depend on the percentage of F1. The uranium concentration increases with uranium grade when the percentage of F1 is higher than 25%. The uranium concentrations increase firstly and then decrease with uranium grade when the percentage of F1 is less than 10%. Finally, the relationship models between initial concentration and the grade of F1, and the uranium peak concentration and the total grade of F1-F4, time of the uranium peak concentration were established respectively. Based on the uranium chemical fraction, the results can provide support for the selecting of leaching agent, the determination of application time and the prediction of uranium in-situ leaching process.