Abstract: A particle image velocimetry (PIV) was used to measure the water flows behind triangular multi-orifice plates of five different types, and an analysis was made on the effects of different orifice sizes (side length = 2.6, 4.0, 5.1 and 6.7 mm), orifice numbers ( = 9, 16, 25 and 64) and orifice arrangements (checkboard and staggered) on time-averaged velocity, turbulence intensity, and turbulent shear stress of the flows. Results showed that the cross-sectional profiles of these flow quantities took a zigzag shape, and that the turbulence mixing and shearing of the multiple-jet flows behind the plates could be intensified and even flow cavitation could be generated by appropriately decreasing the orifice size, increasing the number of orifices, or taking staggered arrangement. The strongest intensification in all the test cases occurred at the staggered arrangement of 25 triangular orifices with their side length of 4mm, achieving the greatest velocity gradient and most intense mixing and shearing effects.