Objective:To simulate the urinary tract environment in vitro and observe the local thermal effects generated by the holmium laser when it is continuously emitting under different mode settings, working medium and perfusion speed.Methods:This study was conducted from March to December 2019. Static medium model: Under normal pressure, 25℃ constant temperature and 50% humidity, a glass test tube with an inner diameter of 1cm and working medium of 1ml was placed into a beaker containing 300ml of 37℃ constant temperature water, and a 550 μm laser fiber was placed in the working medium in the test tube. The laser was continuously emitting for 60.0 seconds, and the temperature of the water in the test tube was continuously recorded using a temperature measuring instrument. The laser working mode was set as dusting, fragmenting, and "popcorn" mode, the energy was set at 10-20 W, and the working medium was normal saline, distilled water, and 5% mannitol solution. Flow medium model: In the same environment, the same optical fiber and temperature probe were placed in a 6mm flush tube, and the laser was continuously fired and continuously perfused with saline. The flushing speed was controlled between 100 ml/h and 1 200 ml/h, and the water temperature change during laser emission was recorded. The real-time temperature changes around the fiber tip with different modes, different media, and different perfusion rates were analyzed.Results:Static medium model: After the holmium laser was continuously fired for about 6.0±1.2 seconds, it exceeded the safe temperature of 43℃ , reached the plateau temperature in about 27.6±2.1 seconds and drop to the safe temperature after stopping excitation for 38.2±2.4 seconds. The plateau temperature dusting group > "popcorn" group > fragmenting group ( P<0.01), of which the dusting group(78.67±0.45)℃ (20 W) was the highest and the fragmenting group (55.67±0.22)℃ (10 W) was the lowest. The temperature of 5% mannitol solution (73.92 ± 0.44) ℃ was the lowest among the three experimental working media, which was (75.57±0.14)℃ of distilled water group and (78.67±0.45)℃ of normal saline group (0.4 J×50 Hz, 20 W). Flow medium model: The perfusion rate of 800ml/h can ensure that the continuous emitting of the holmium laser remains at a safe temperature (40.96±0.36)℃. It only took 7.0±1.0 seconds to decrease to the initial temperature after stopping emittion. Conclusions:Under the same total power, the high-energy-low-frequency fragmenting lithotripsy mode has a relatively lower thermal effect. Under the same total power, the thermal effect of holmium laser emittion is relatively lower in the environment of 5% mannitol solution. Perfusion of ≥800ml/h can effectively reduce the local high temperature caused by the thermal effect of holmium laser.