For the problem of erosion-corrosion in oil pipeline system, used ANSYS FLUENT software, by changed the inlet velocity, the particle mass flow rate and the particle diameter, conducted numerical simulation for flow field distribution and severe erosion area of 90° elbow pipe. The results show that: with the increase of inlet velocity, the pipe erosion rate increases gradually; with the increase of particle diameter, the pipe erosion rate decreases; with the increase of particle mass flow rate, the pipe erosion rate increases linearly; and there have interaction between the three erosion factors of inlet velocity, particle mass flow rate and particle diameter.