The surface roughness of Si film is an important parameter to describe its quality. In order to investigate the correlation between the surface roughness of silicon film prepared by pulsed laser deposition and gas pressure, by using Lambda Physik XeCl excimer laser, nanocrystalline silicon film is deposited in different inert gas atmospheres such as He and Ar, by using Tencor Instruments Alpha-Step 200, the surface roughness of the sample is measured. The results show that with increasing gas pressure, the roughness of Si film first increases and reaches its maximum and then decrease, furthermore, the numerical value in Ar is less than that in He. The roughness maximum strongly depends on the inert gases used. For the heavier gas, Ar, the maximum is 11% higher than that in the case of very-low pressure, for the gas He, the corresponding values are 314%.