The mobility of heavy metals including Cd, Cr and As, among sediment, pore water and overlying water under different hydrodynamic conditions in 15 d was analyzed with hydrodynamic flumes. Three velocities were designed as 4.01 cm/s for slow flow in Flume A, 12.70 cm/s for middle flow in Flume B, and 20.23 cm/s for fast flow in Flume C. Results show that: 1) Increasing the velocities of flow can promote the release of heavy metals; 2) As of pore water presented higher concentration, which shows the mobile trends of As are from pore water to overlying water; 3) Sediments suspended are the main reason for the increase of concentration of heavy metals in the overlying water. Compared with the static condition, hydrodynamic conditions significantly affect the mobility of heavy metals. And the changing characters in each flume are different for each kind of metals in different kinds of medium (overlying water, pore water, and surface sediment). Moreover, the extent of hydrodynamic impacts on the mobility of heavy metals is overlying water>sediment>pore water.