Abstract: Underground oil viscosity is high(which reach to 800 mPa·s) in south area of Nanpu 35-2 oilfield in Bohai oilfield,problems existed as single well low production capacity,small recovery speed,oil well water cut rise quick in transitional zone.In this paper,weak gel is used to improve development effect.Through dynamic analysis,the main reason for water cut rising quick is that crude oil viscosity is large,fluid ratio is big.Started with the water flooding oil theory,using reservoir engineering method,systematically discuss the low efficiency of water driving in south area.Weak gel flooding oil is proposed to improve water-oil fluid ratio,and enhance water flooding oil volume and parameters,which reach the target of enhancing recovery.Field test shows,this method has good effect for improving water flooding and keep formation energy.