The purpose of this study is to estimate ablated crater depth with sufficient numerical accuracy when multishot channels of ultra-short pulsed laser are executed formicro drilling processes on thin glass plates. In this analytical model, the plasma model, in which the free electron density and the complex dielectric function of the Lorentz model are evaluated, is applied to estimate the ablated regions and the regions damaged by laser ablation when glass is considered to be a dielectric material. The absorption coefficient and the threshold fluence are important parameters in the evaluation of the ablated crater depth and ablation rate. The parameters obtained in this numerical analysis are in agreement with the experimental results and are computed quantitatively to several laser irradiation conditions. The experimental results and analysis results are examined for multi-shot channels. In an experiment involving laser ablation using multi-shot laser beams, ablation rates for the initial shot are lower than subsequent ablation rates. The effectiveness of the modified absorption coefficient and modified threshold fluence for initial shots is confirmed for the reduction of ablation rate.