Abstract: Jidong Nanpu shallow land reservoir is complex fault block reservoir.With the increasing of horizontal wells,the number of oil wells with high water cut has accounted for90%of the total number of horizontal wells in 2010,which seriously affected the development effect.CO2 huff and puff test on heavy oil horizontal well has gained good effect on water control and oil increment in October 2010 and gradually is applied to the directional well,thin oil well with significant effect.According to the classification of the CO2 effect,the typical wells are analyzed,which identified the main causes of good CO2 stimulation effect or not.CO2 has good stimulation effect in the wells where construction site is relatively high,the degree of recovery is low,oil saturation is high and reservoir seal is better.While the CO2 has bad effect in the wells where it is near the oil- water boundary,adjacent wells in high position,the production rate is high,construction site is low,residual oil saturation is low and reservoir seal is not good.Analysis on the typical wells can provide reference and guidance for future study and formulation of water control and oil increase measures for the same type of reservoir.