Conglomerate reservoirs are strongly heterogenous and complex in pore structures，and the microscopic percolation system presents sparse network-non-network characteristics. Conventional chemical flooding can easily cause chemical agents to protrude along high-permeability layers and the medium- and low-permeability layers are difficult to exploit，leading to limited swept volume and low oil displacement efficiency. Through the explorative research in a conglomerate reservoir in Block K7，Karamay Oilfield，Xinjiang，an oil recovery method of“cascaded injection and graded production”is proposed，dramatically enhancing oil recovery. This method combines the reservoir percolation theory and core analysis.Firstly，a calculation model of the decline rate of inter-well pressure gradients is constructed，which is affected by reservoir heterogeneity. Secondly，the major influencing factors of the percolation resistance to the chemical agent medium are determined，and a calculation formula of percolation resistance is created on the basis of the microscopic pore structure parameters of the reservoir，the mass concentration of polymer solution，and the polymer molecular weight. According to the theory that oil displacement media can flow in reservoir only when the displacement pressure gradient is greater than percolation resistance，the high-resistance chemical agent system can only enter the large pore-throat permeable layer at a constant injection rate and a fixed injection-production well spacing. As the system continues to advance，the displacement pressure gradient plummets and the chemical agent system can stay and block the large pore-throat permeable layer. At this time，the mass concentration of the system can be reduced in a cascaded manner，and the resistance coefficient can be lowered，so that the system can enter permeable layers at different pore throat levels sequentially，and the remaining oil in different microscopic pore spaces can be produced in grades. This theory has achieved good application effects in the field test of Block K7，the oil recovery enhanced by 15.9% in the chemical flooding stage of the reservoir.