The excimer laser has shown a rapid development from the laboratory to its current clinical use for refractive surgery. Operating at 193 nanometers, the excimer laser is able to sculpt the corneal surface meticulously, altering the surface optical architecture to correct refractive errors. Such surgery is achieved with minimal mechanical and thermal effects upon the remaining corneal tissue. We studied laser and tissue interactions, investigated the effect of laser spot size and beam profile on the outcome of corneal surface smoothness and determined the relationship between the fluence of ArF excimer laser and the cornea ablation rate. The block diagram of ophthalmic excimer laser system and it's principle have been described. Finally, we tested ablations on polymethylmethacrylate (PMMA) and applied them to clinical operations with the satisfied results.