The application of side channel spillway in Headworks is vel)' suitable for highland projects which have strait river-bed, high slope, quickly concentrated flood... In case of big flood, side channel spillway can not drain off the water, People need build more other flood spillways. Recently, in Vietnam, there have not researched about side channel spillway combine with other flood spillways yet, especially (bottom outlet) culvert spillway. Therefore, the following research results will express somewhat hydraulic regime of the combination spillway work.