In this work, a numerical model to predict the heat accumulation of fused silica induced by ultrafast laser scanning is put forward, which is composed of an ionization model and a steady electromagnetic model. The ionization model is to obtain the energy deposition induced by single laser pulse. Subsequently, the temperature evolution during ultrafast laser scanning is estimated through the superposition of the heat impact by each laser pulse. The ablated profile from experiments is compared with the predicted profile of heat-affected zone (HAZ) to illustrate the nonthermal processing window, which is validated by Raman spectrum. The analysis of the parametric sensitivity on heat accumulation is carried out, and the laser pulse energy is the dominating factor.