Abstract: The Ban-2 oil group of Banqiao area is a typical condensate oil and gas reservoir.There are many difficulties in develop adjustment because of the complicated percolation and water flooding characteristic.So the experiment of gasliquid two phase flow was developed.The results show that gas-liquid fluid would be phase transition and mass transfer along with the changes of flow state and pressure.Fluid volatile have a relationship with the flow speed , fluid state and pressure.Reduce pressure will be beneficial to liquid volatile produce gas.The experimental results also show that the bubbles would be resistance for the crude oil flow in the step down water flood recovery process , when the pressure less than critical saturated pressure.The right time to water injection is the pressure reduced to more than87%of the bubble point pressure.In addition , the strength of the gas effect has obvious influence on the formation and distribution of remaining oil.