A new type of tetrahedron permeable frame was proposed based on the concept of fish shelter, and experiments on the flow characteristics around the protected area were conducted using acoustic doppler current profilers(ADCP). Then, the influences of overhead rates on the flow structure and hydrodynamic characteristics were discussed. The experimental results show that the difference of velocity distributions between the top and bottom of flow is more obvious. The flow velocity of the frame layer is obviously reduced, and the decrease rate of the flow velocity increases with the decrease of the overhead rate. An inflection point appears in the turbulence intensity distribution, and its position has a distinct correlation with the overhead rate. In addition, the turbulence intensity increases with the decrease of overhead rate too. There is a turbulent convergence zone near the bottom of the protective zone, and the turbulence intensity of this zone decreases with the decrease of the overhead rate.