Cavitation effect induced by holmium laser pulses firstly happens when fiber-transmitted holmium laser pulses ablate biological tissues under liquid environment. Then liquid thermodynamics can directly determine the overall mechanisms of laser-tissue interaction. Free-running holmium laser pulses with pulse duration of 300 μs ［full width at half-maximum (FWHM)］ and wavelength of 2.12 μm are used to ablate calculus consisting of calcium oxalate monohydrate (COM) and uric acid (UC) constituents. After irradiation the crater tomographic image is measured by optical coherent microscopy (OCM) technology to quantify width, height, and volume. Experimental results indicate after multi-pulse irradiation with the same energy of a single pulse, the difference of the surface tomography is much more obvious. The ablation efficiency in water is much higher than that in air. This indicates that liquid can contribute to the laser-substance interaction.