Nd2O3 film is a functional film with great potential application value. In this paper, thinNd2O3 film was prepared on the surface of Si substrates using RF magnetron reactive sputtering. Nd2O3 film with different crystal structures were controlled by changing the deposition temperature. The results show that the Nd2O3 film with a cubic structure can be obtained at 150 °C, while a hexagonal structure appears at 250 °C and above. The refractive indices of the cubic and hexagonal Nd2O3 films were 1.736 and 2.130, respectively. Moreover, the principle of the influence of deposition temperature on the refractive index of the film was illustrated. The hardness and the elastic modulus of the cubic Nd2O3 film were 6.3 GPa and 102 GPa, respectively, which are much lower than the 9.9 GPa and 145 GPa of the hexagonal Nd2O3 film. In addition, with a double-sided cubic Nd2O3 film, the maximum transmittance of the diamond film reached 87.54%. The results show that the Nd2O3 film is an anti-reflection film suitable for optical applications.