The laser drilling holes processing experiment was conducted on the silicon under the radiation of a 1 064 nm nanosecond repetitive pulse laser. Variation rule of holes′ diameter transferring with laser pulse number and the depth of the holes could be both observed through this experiment. Meanwhile it analyzed the thermodynamic process of pulse laser irradiating silicon as well. The result shows that being confined by the narrow hole, the hot plasma expands rapidly inside the channel. It transmits a large fraction of its energy to the hole walls by radiative and convective heat transport, thereby contributing to the radial expansion of the hole. The hole depth growth rate have linear increase with pulse number when the pulse number is under 6, after that it becomes slower and slower until remain stable, which is mainly due to plasma shielding effect.