In order to study the impact of different junction angles and discharge ratios on the backwater characteristics at open-channel confluences, a three-dimensional numerical model was established by using the Volume of Fluid(VOF)method for the free surface capture and adopting the Reynolds Stress Model(RSM)for the governing equations closure. The 3D pattern of backwater was analyzed after the simulations of 21 combined conditions for 3 different discharge ratios and 7 different junction angles. The results indicate the raising of water level in the upstream area and the dropping of water level in the junction area because of the tributary convergence. Under a same discharge ratio, the upstream water level increases as the junction angle increases, and the drop of the water surface in the downstream becomes more obvious. The minimum and maximum ratios of the upstream water depth to downstream water depth were calculated, which indicate that both the minimum and maximum depth ratios increase with a greater junction angle or a smaller discharge ratio among the ranges of junction angle and discharge ratio in the current study. The variation range of the depth ratio was also analyzed. Under a same discharge ratio, a greater junction angle leads to a larger variation range of water level around the junction area. Under a same junction angle, a greater discharge ratio leads to a smaller variation range of water level around the junction area.