Silicon monoxide (SiO) thin films is one of the most commonly used optical film in short-wave and medium-wave infrared. High packing density for enhancing the spectra stability and the quality of the optical thin film elements is extremely important. Used 99.99% purity of the SiO bulk materials, SiO thin films were prepared by molybdenum boat thermal evaporation in 5×10－4 Pa vacuum pressure at different deposited temperature, while deposition rate was monitored and demonstrated at 1.2~1.5 nm/s by quartz crystal oscillation controller. The thickness of the thin films on silicon substrate is about 2.2~2.4 μm. Used the Fourier transform infrared spectrometer to test the spectral characteristics of SiO thin films before and after the thin film suck tide, and according to the wavelength deviation dispersion theory, calculated the packing density. The results show that as the deposition temperature increased, the packing density increased, from 0.91 at room temperature to 0.99 at 250 ℃.