In general, there are many bifurcations in natural rivers. When the oil spilled accident occurred at the upstream of bifurcation and was not controlled in time, the pollution scale would be expanded and the treatment would become harder as the oil slick entered into braided river driven by combined water and wind. To Study the separate law at the bifurcation in rivers, a two-dimensional numerical simulation model of oil spilled was established by oil particle model theory on the basis of two-dimensional hydrodynamic model. The quantitative relationship between the oil separate ratio and the flux ratio, velocity ratio, width ratio was obtained driven by water. The wind effect on the proportion of oil separate was also discussed based on the oil spilled numerical simulation. This study will provide technical support for forecast and response of oil pollution in braided rivers.