This study investigates how different cooling water flow velocities affect the cooling performance of copper plates in a water-channel crystallizer. An experimental setup was developed and combined with numerical simulations to analyze the heat transfer and flow behavior of the copper plates. The convective heat transfer coefficient on the water channel wall and the hot-face temperature of the copper plates were quantitatively assessed. Experiments showed that, under a heat flux of 0.2 MW/m2 and cooling water flow rates between 5.39 to 9 L/s, the relative errors between the numerical simulation results and the experimental data regarding the average convective heat transfer coefficient are all within the range of 7.5% to 7.8%, each 1 m/s increase in average cooling water velocity raised the convective heat transfer coefficient by 3.21 kW/(m2•K). This confirms that cooling water velocity is a key factor influencing the mold's cooling efficiency. Numerical simulations, conducted under a 1 MW/m2 heating flux boundary condition, indicated a similar trend: every 1 m/s increase in water velocity improved the convective heat transfer coefficient by 3.85 kW/(m2•K). The heat transfer coefficient is positively correlated with flow velocity, yet the magnitude of this increase becomes less significant at elevated flow rates compared to lower ones. Additionally, this study establishes a Power function relationship correlation between the Nusselt number (Nu) and the Reynolds number (Re) of the water flow within the channel. These findings offer a theoretical foundation and practical guidance for optimizing the cooling performance of copper plates in continuous casting molds.