Thermodynamics and kinetics for the preparation of Sm2Fe17 alloys by reduction-diffusion (R-D) method in Ca-Sm2O3-Fe System were investigated. With increasing reaction temperature, it is found that the reaction rate of R-D and the amount of Sm in the Sm2Fe17 alloy increase, and the increased amount at lower temperature is higher than that at higher temperature. Moreover, results from contracting core model show that the peritectic reaction between Sm and Fe is a rate-determined step in the whole R-D process. The apparent activation energy and the pre-exponential factor for this reaction are 73.74 kJ·mol-1 and 7.79×10-3 respectively.