Low Froude number hydraulic jumps always occur under the conditions of large discharge with low hydraulic head, causing the risk of scour damage to the downstream riverbed and slopes. This paper addresses the characterization of low Froude number jumps on cases of different slopes of end sill in a hydraulic project using numerical analysis. The results show that under low Froude number inflow, submerged transition flow is formed in the stilling basin, and the flow field of the submerged transition jump is divided into core zone, developing zone, and backflow zone in the horizontal direction. The core zone is then divided into jet inner layer, jet outer layer, roller inner layer, and roller outer layer in the vertical direction based on the velocity characteristics. The time-mean pressure increases and the bottom velocity decreases along the course in all types of stilling basins. The steepening of the end sill slope causes the starting plane of the roller to move upstream and ending plane to move downstream, resulting in a longer roller. The gradient of the underflow velocity in the end sill slope section is 0 when the slope ratio is 1∶3, it is negative when the slope ratio is less than 1∶3 and positive when the slope ratio is greater than 1∶3. This is because the steeper slope reduces the resistance of the end sill to the water in the direction parallel to the slope, resulting in a gradual increase in velocity gradient. These findings can provide a reference for the design of stilling basins in similar projects.