The transport dynamics of the ablated particles is simulated via Monte Carlo simulation. The influences of ambient gases (He, Ne, and Ar dummy gas) on velocity splitting of the ablated particles under 100 Pa are investigated. The results show that the velocity splitting appears in four types of gases. The formation times of velocity splitting of the ablated particles decrease in sequence of He, Ne, dummy gas and Ar. The influences of the mass and radius of ambient gas molecule on the velocity splitting are also investigated. The formation time of the velocity splitting decreases with mass/radius of ambient gas molecule increasing. The intensity is the smallest when the two velocity peak intensities are equal. The formation time of velocity splitting is explained by the underdamping oscillation model and the inertia fluid model. These results give a good foundation for the further study of the Si nanoparticle growth.