Considering the short-range interaction of multi-particles, we have employed the equivalent plate conductivity model to simulate the phase transition of solid-liquid electrorheological(ER) fluids in flow process. We also devised experiment to observe the phase transition of ER fluids. The conclusions show that under the certain pressure the ER fluids begin to flow, here the flow is the two-phase flow. But when the strength of external electric field reaches a certain threshold value, the particles in ER fluids stop flowing, so the flow of ER fluids changes into one-phase flow, the phase transition happens. The phase transition observed in our experiment complies with the simulation fundamentally. The threshold strength of external electric field increases with the increasing pressure, and decreases with the concentration of particles in ER fluids.