Abstract: To divert the water flow from the channel into the field for irrigation, a diversion port is often set up on the side of the main channel for drainage. When the water flows from the channel into the diversion port, a curved water flow is formed. In addition, the sudden contraction of the diversion port section causes a drastic change in the flow state of the water in the diversion area, forming obvious high-speed and low-speed zones. This uneven distribution of flow velocity will have an impact on the diversion flow rate and sediment distribution. Due to changes in flow rate and pipe diameter, the water distribution side pipe often experiences a state of non pressure. To investigate the influence of non pressure side pipes on the hydraulic characteristics of the channel diversion zone, physical model experiments were conducted to study the three-dimensional flow velocity, turbulence intensity, diversion width, and diversion ratio of the channel diversion zone under different filling degrees.The experimental results indicate that the distribution of three-dimensional flow velocity and turbulence intensity at the channel separation zone is not changed by the non pressure pipe flow under different filling degrees, but only affects the magnitude of three-dimensional flow velocity and turbulence intensity. From the bottom of the canal to the water surface, the longitudinal, transverse, and vertical flow velocities all show a gradually increasing trend. From upstream to downstream of the water outlet, the longitudinal average flow velocity gradually decreases, while the transverse and vertical average flow velocities first increase and then decrease. The longitudinal, transverse, and vertical turbulence intensity first increases and then decreases, and the turbulence intensity is higher in the area directly facing the pipeline inlet. The horizontal and vertical flow velocity values facing the diversion port are relatively high, thereby increasing the diversion flow of the pipe. However, the vertical flow velocity value at the diversion port decreases, which reduces the sediment carrying capacity of the water flow near the diversion port. At the same time, the horizontal and vertical turbulence intensity in this area is relatively high, and the water flow is prone to form a circulation at this location, making it easier for sediment to settle and accumulate in the diversion area.As the filling degree increases, the longitudinal average flow velocity and turbulence intensity, as well as the vertical average flow velocity, of each section of the channel decrease, while the transverse average flow velocity and turbulence intensity, as well as the vertical turbulence intensity, increase. The diversion width of non pressure pipe flow increases with the increase of filling degree, and unlike rectangular diversion ports where the diversion width gradually increases from the water surface downwards, the variation law of diversion width of non pressure pipes along the water depth direction is more complex. The original formula for dividing water width is no longer applicable to non pressure pipe flow. When the filling degree is less than 0.5, the dividing width gradually decreases from the water surface downwards. When the filling degree is greater than 0.5, the dividing width first increases and then decreases from the water surface downwards When the flow rate of the main channel is constant, the diversion ratio increases with the increase of filling degree; When the filling degree is constant, as the flow rate of the main channel increases, the diversion ratio decreases. Therefore, in the actual water supply process in the field, when the inflow of the main channel is constant, the water depth in the main channel can be changed to increase pipeline diversion and improve pipeline flow.The research results of this article can provide certain technical support for the design and maintenance of field canal water diversion projects.