Class III reservoirs in Daqing Oilfield account for nearly half of the total reserves in La-Sa-Xing Oilfield of Daqing Placanticline，which have geological characteristics including thin thickness，low permeability，poor connectivity，and serious heterogeneity. For the synchronous displacement of high-and low-permeability oil reservoirs by chemical flooding and balanced reservoir efficiency，the displacement experiment with a laboratory plane model was carried out and the development effects of enhanced oil recovery（EOR）technology were compared at different production modes in Class III reservoirs. As a result，the staged chemical flooding production mode was selected and applied in oilfields.In the first stage，polymer flooding was performed in thin and poor oil reservoirs with effective thickness less than 0.5 m and effective permeability less than 0.05 D and untabulated oil reservoirs. In the second stage，commingled weak-alkalinity ASP flooding was carried out in other oil reservoirs by supplement perforation. The results show that in laboratory experiments，staged polymer flooding for medium-and low-permeability oil reservoirs registers ultimate recovery of up to 65.8%. The field application of staged chemical flooding in Gaotaizi reservoir of Beierdong Block indicates that the overall ultimate recovery is expected to increase by more than 12% in the test area，and remarkable results have been achieved.