Abstract: The giant Daqing oil field is an anticlinel structure with an extensive area.It is a multi-pay field producing from heterogeneons sandstone reservoir characterized by higher viscosty of crude,small initial formation and saturation pressure difference and inactive edge water encroachment. With the application of pressure maintenance through selective injection of multiple zone,wells are kept on flowing vigorously under high producing potential.A clear understanding of the oil and water distribution in the reservoirs after water injection is obtained by careful study of the heterogeneity of the reservoir and frequent selective well testing. In addition,new techniques(the so-called "Separate layer" technique) have been developed arid applied in the field to enhance well productivity by selective fracturing,selective plugging,use of dual string etc,to adjust oil and water distribution so as to increase the volume in the reservoir. After nearly twenty years production,the reservoir pressure of the field is maintained at nearly the same initial pressure level,with no decline of average daily production per well,and with the rate of recovery maintained at the 2% level.The result of development has been satisfactory.