A side sluice gate is a metering diversion structure set into the side of a channel with the purpose of allowing part of the flow to spill through the side. Side sluice gates can be used in irrigation, land drainage, urban sewage systems, sanitary engineering and as head regulators of distributaries. The flow through a side sluice gate is a typical case of spatially varied flow with decreasing discharge. In this type flow the amount of discharge reduce along the main channel and pay attention to type of flow at upstream of sluice gate (subcritical or supercritical) profile of water surface in neighborhood of sluice gate and also control section will be different. In this study the hydraulic characteristics of 12 physical models of side sluice gate in subcritical flow were considered. For this object discharge coefficient, profiles of water surface, variations of specific energy along of side sluice gate, three-dimensional velocity distribution in main channel, direction of velocity vectors, angles of output jet along sluice gate and variations of velocity under different conditions of flow were investigated. The results showed that the highest values of longitudinal velocity (V x ) at the distance of 3 centimeters from side of channel occur near the beginning of the side sluice gates while the lowest values of this component of velocity would take place at the end of the side sluice gate. After the passing of flow at sluice gate V x again increases until to get the constant value. Variations of V x along the side sluice gate at distance of 10 centimeters from side and central line of channel is similar to distance of 3 centimeters from side of channel but their variations are decreased. Investigation the vertical velocity (V y ) at the distance of 3 centimeters from side of channel showed that before and after the side sluice gate its values is negligible and at the present of side sluice gate increase severely. The maximum of V y was observed in upper edge of side sluice gate and direction of V y movement at the all of points is from the water surface toward channel? s floor. The values of V y at distance of 10 centimeters and central line of channel are negligible. Investigations the values of cross velocity ( V z ) showed that this velocity component also has low values at the before and after side sluice gate and at the present side sluice gate the maximum value of V z occurs at the channel? s floor. The values of V z at distance of 10 centimeters and central line of channel are lower as compare to the distance of 3 centimeters from side of channel. The effect of Froud number variations, opened and length of side sluice gate on velocity profiles investigated at three dimensional. The re sult show that the increase of Froud number cause the decrease of V x from upstream to beginning of side sluice gate and increase of V x from side sluice gate center to downstream. Also the Increase of Froud number cause the decrease of V y and V z at the around of side sluice gate. While the increase of amount of opened and length of side sluice gate causes the increase of V x from upstream to beginning of side sluice gate and decrease of V x from side sluice gate center to downstream. Also the increase of two parameters cause the increase of V y and V z at the around of side sluice gate. In this study presented the equations for determination of the side discharge, side discharge coefficient and angel of output jet. Keywords : side sluice gate, three dimensional velocity, discharge coefficient, water surface profiles, angel of output jet.