Abstract: To study the thermal pollution caused by cooling water discharge from Bayuquan thermal power plant, in-situ measurements of the tidal currents and the heat diffusion in the surrounding area of the power plant were conducted in this study.Three-dimensional finite element numerical model RMA-10 was also used to simulate the three-dimensional temperature rise field caused by cooling water discharge from the power plant.The major findings are as follows:(1) The temperature distribution is significantly affected by the cooling water discharge.The model predicted average area with over 1℃and 4℃temperature rise in the surface is 0.648 km² and 0.199 km², respectively; (2) The extent of cooling water discharge appears to correlate directly with the tidal currents.Over a tidal cycle, the extent of the thermal plume during the low tide is larger than that during the high tide; (3) The vertical distribution of temperature rise is not uniform, and the area with temperature rise in the surface is 2 to 4 times larger than in the bottom, suggesting that cooling water diffuses mainly in the upper layer due to the buoyancy effect.As such, the commonly used two-dimensional model may not be suitable for simulating cooling water discharge, and three-dimensional model is preferable in such a case.