This study aims to investigate the physics mechanism of urine splashing caused by men when using urinals. The research methods include: 1. analyze laminar and turbulent flow with strobe light and time-lapse photography, water flow laser guide experiments, Tracker software and Reynolds number software. 2. Make a urine simulator and measure its inner air pressure and the force of water flow and rebounding water generated by the urine simulator on the wall of the urinal. 3. analyze the splash area and distribution with Monte Carlo method and Image J software. The results show that the flow rate is the main reason that influences the splash of turbulent flow and rebounding water. When the urine flow rate is below 15 mL/s and the distance between users and the fly image is below 20 cm, the turbulent splash is minimized. When the urine flow rate is above 15 mL/s and the horizontal urination is at 30 cm, the rebounding water is minimized. For a user taller than 170 cm, horizontal urination with 25 mL/s flow rate causes the smallest splash area and distribution in both kinds of tested urinals. At last, aiming at the urinal drain when urinating results in the largest splash area and distribution. This study also discusses the improvement of the research method of urine splash.