Abstract: High-speed turbidity currents are very destructive and threaten the safety of seabed constructions. An important channel for turbidity currents to move to the deep sea is submarine canyons, of which many have multiple branches. Once a branch meets the canyon with turbidity currents, the sand content and the velocity of turbidity currents could be increased, and so the destructive power. We studied the changes in sand content and movement velocity of turbidity currents in branch canyons converging into the main canyon, to which the scenario of turbidity currents in main-canyon-only was compared. Result show that the height, sand content and velocity of turbidity currents were increased at the head when confluence occurred, and decreased after the confluence occurred. However, the sand content and the velocity were still larger than those without confluence. This study provided guidelines for site selection and velocity calculation for field monitoring when turbidity currents confluence occurs in branch canyons.