The thermal–hydraulic performance of flame deflector in a reduced-scale rocket engine testing platform with different water spray schemes is analyzed. The standard k-ε turbulent model and Eddy-Dissipation Concept (EDC) model are applied to solve the characteristic of the flow and combustion and the discrete ordinates (DO) model is adopted to simulate the thermal radiation. Model validation shows that the predicted results are in good agreement with the experimental data. In addition, the flow and temperature field of the exhaust gas impinging on the flame deflector under different water injection location, mass flow rate, hydrogen ratio and vertical panel height are numerically investigated. The results reveal that the scheme of centre water spray performs better than other schemes in terms of maximum and area-averaged temperatures. In terms of the flow performance, the case of annulus water spray performs best, followed by centre water spray and bottom water spray worst. With the increase of hydrogen ratio, the reburning of hydrogen results in the amplification of the high-temperature region in the flame deflector. The temperature on the bottom surface decreases gradually but the temperature on the vertical panel increases with the increase of the vertical panel height.