Abstract: Outstanding achievments have been obtained in the application of water flooding for production of multizones in the Daqing oil field.From practice,it shows that the solution of the following basic problems is key to the effective development of an oil field by water flooding.1.To have a scientific and valid development program,including a network of injection and production wells,a monitoring system of reservoir performances,a production technological system and a surface construction engineering system: The whole program should be organically coordinated and well planned for the systematic development of the oil field by water flooding.2.To conserve sufficient reservoir energy and establish a pressure system to ensure replenishment and full utilization of the energy and to prevent the occurrence of three-phase flow in the reservoir so as to actively adjust the pressure difference for driving oil.3.Based on the status of reserve,to develop production technology by injecting more water into the reservoir in such a way as to control water porductian from the oil wells and to keep more water underground in order to increase the sweep volume of flood and effectively raise the recovery factor.4.In accordance with the heterogeneous nature of reservoir and the character of oil and water movement,to fix the main objectives of development of one period and devise ways to prolong the period of stabilized output successively in a planned way.