<p>Different lasers are used in intra corporeal lithotripsy. They differ in their wavelengths, pulse durations, and pulse energies. One of the most recently used laser in surgery is the Ho:YAG laser. It is introduced for both of the soft tissue ablation and lithotripsy applications. The use of this laser in lithotripsy is increasingly widespread, because it can fragment all stone types and produce tiny fragments, which can easily pass through the urinary tract. The mathematical models of this laser interaction with two urinary stones are considered and studied in this paper. They are based on the thermal effect calculations of Ho:YAG laser on these stones. The crater volumes and crater depths in both of the calcium oxalate monohydrate (COM) hard stone and uric acid (UA) fragile stone were calculated as a function of the exposure radiant laser energy, number of pulses and pulse durations of thisHo:YAGlaser. The achieved theoretical results are close to other published practical results. It was found that the absorption of laser energy by the urinary stones is the most effective parameter, which makes the theoretical results comparable to the practical results.</p>