Due to the oilgaswater threephase flow is extremely complex, the threephase hybrid interface is weak of stability, different delivery conditions exist a variety of flow patterns. Using the VOF model simulation, the mock object was oilgaswater threephase flow in mutation tube, studying the fluid flow in pipe when the parameters(volume gas fraction, oil viscosity and velocity) was different, thus it gotten the corresponding phase distribution nephogram. Through analyzing the results showed that the gas volume fraction and velocity had great effect on mutiphase flow pattern. The effect of crude oil viscosity on flow patterns was not very obvious. The size of the pipe diameter also affected the flow pattern.