Abstract: This paper studies the changing rule of rare earth separation coefficient of unsaponifiable extraction in P507-N235 system. The results show that the separation coefficient of La/Ce improves by adding N235 to P507 and it increases with the adding amount of N235. The La/Ce coefficient increases with the adding comparable O/A. The appropriate mixing and extracting time should be controlled in 8 min. Comparison experiment results show that the separation coefficient of rare earth in P507-N235 system is generally higher than that of the P507 system.