Abstract: This paper simulates the oil-water two phase flow in oil reservoirs under constant pressure in accordance with the flow characteristics of heavy oil.It firstly injects heavy oil and formation water into the artificial core of saturated oil at the same time,and then observes the flow characteristics of them.The result shows that liquid production is determined by the injection pressure.That is,the higher the injection pressure gradient gets,the more greatly the water production increases.Oil production,however,has a little change.The experiment shows that it is not appropriate to enhance oil recovery relying on increasing injection pressure.The injection pressure should be optimized to reduce cost on ground construction.