To investigate the hydrodynamic characteristics around rectangular multi-piers, PIV (particle image velocimetry) technology was utilized to conduct flow experiments on configurations with different longitudinal and transverse spacing ratios (T/L, B/D) including arrangements of four rectangular piers and two parallel rectangular piers. The flow field distribution, turbulence intensity, and reynolds stress were analyzed. The results show that when 1.5≤T/L = B/D≤2.5, a boundary at X = 200 mm causes the time-averaged velocity to be higher for the arrangement of four rectangular piers compared to the two parallel rectangular piers, with the latter arrangement exhibiting higher velocities downstream. The turbulence intensity for the two parallel rectangular piers exhibits a generally M-shaped distribution across the section, whereas in the arrangement of four rectangular piers, the symmetry is less apparent, and the turbulence intensity is overall lower than in the two-pier configuration. When T/L = B/D = 1.0, the Reynolds stress on both sides of the four rectangular piers follows an alternating antisymmetric quadrupole distribution. As the spacing ratio increases, the center points of the downstream pier's quadrupoles shift upstream. The findings reveal the flow characteristics of rectangular piers under varying spacing ratios, providing valuable insights for pier arrangement in similar hydraulic engineering projects.