The breakthrough of gas usually occur during low permeability reservoir development,that lead to recovery efficiency fall.This paper worked over a new displacing technique,which droping water on rock core when we proceeding gas drive.The new displacing technique will increase the filtrational resistance of injected phase, reduce breakthrough of gas. The air pressure dimensionless parameter will increasing as long as the gas fluid ratio decreasing.The rising of frequency of droping water will result in air pressure dimensionless parameter increased,so does filtrational resistance.