Nanocrystalline Mg2Si thin films were prepared on sapphire substrate by radio frequency (RF) magnetron sputtering using Mg2Si sintered target. The effects of sputtering power (90 W to 140 W) and sputtering time (10 min to 60 min) on structure and resistivity of Mg2Si thin films were investigated. The results show that with the increase of sputtering power, the XRD diffraction peak of the sample gradually increases. However, when the power exceeds 100 W, elemental Mg segregation appears in the samples. With the increase of sputtering time, the XRD intensity of the sample first increases and then decreases. When the sputtering time is 40 min, the XRD diffraction peak of the sample is the strongest. With the increase of sputtering time, a weak MgO diffraction peak appears in the sample. All the samples show the characteristic Raman peaks of Mg2Si crystal, namely, the F2g mode near 256 cm-1 and the F1u (LO) mode near 347 cm-1. With the increase of sputtering power, the resistivity of the sample decreases.With the increase of sputtering time, the resistivity of the sample first decreases and then increases. When the sputtering time is 40 min, the resistivity of the sample is the minimum.