Background: Colonoscopy is a key technique for the prevention and early detection of colorectal cancer. Water-assisted colonoscopy is increasingly adopted due to its potential to reduce patient discomfort. However, the temperature of the infused water plays a crucial role in both procedural quality and patient experience. This study aimed to optimize water-assisted colonoscopy by developing a constant-temperature water infusion system. Methods: A two-dimensional finite element model was established using COMSOL Multiphysics to simulate the heat transfer process between the heating base and the liquid container. The system consisted of a medical-grade 304 stainless steel container, a nichrome heating wire embedded in rubber, and an integrated piping network. Quadrilateral meshing was applied to short-range solid–liquid interfaces and triangular meshing elsewhere, resulting in detailed modeling for both natural heating (27,801 elements) and circulation heating (43,998 elements). Based on simulation results, a hardware platform was developed to deliver sterile water at a constant temperature of 37 °C for digestive endoscopic procedures. Results: Circulation heating demonstrated superior thermal efficiency and more uniform temperature distribution than natural heating. Under ambient conditions (25 °C ), the system reliably maintained water temperature at (37±1)°C . Partitioned meshing enhanced computational precision with a minimum element size of 0.1 mm. Solid-liquid coupling analysis confirmed stable heat conduction during dynamic infusion. The device allows for independent temperature presetting and stepless flow rate adjustment via a control panel. It is also compatible with standard endoscopic systems, thereby enhancing procedural efficiency and safety. Conclusion: The proposed constant-temperature water infusion system model offers a reliable and adaptable solution for water-assisted colonoscopy, improving both diagnostic performance and patient comfort through precise thermal regulation.