The invention discloses a simulation test device and method for absorbing and releasing pollutants from sediments at river junctions. The simulation test device comprises a water circulation device, aflow adjustment device, a sediment laying device and a sampling device. The sediments are laid at the river junctions, equal-height PVC boards are laid on other areas of a water tank, an junction angle is changed by rotating hinges at the junctions of a main stream and branches, pipes are led out from a downstream water tank to return to an upstream main stream and branches, a perforated plate isarranged at a water inlet of the water tank, and energy is dissipated to stabilize inflow in the water tank. The device can further monitor and control the flow of the main stream and the branches. The device can flexibly change the junction angle and the flow ratio of the junctions of the main stream and the branches and is applicable to rivers with different junction ratios under natural conditions; and meanwhile, the device further realizes the self-circulation function in the simulation process, water in a water storage tank can be reused, water consumption can be greatly saved, and the collection and centralized treatment of pollutant-containing wastewater can be facilitated to avoid secondary pollution.