Abstract: The activity ratio of PY24 fault was studied with logging data and 2D and 3D seismic data.It was found that the PY24 fault was very active during the depositional periods of upper Zhujiang Formation,Hanjiang Formation and Yuehai Formation,but silent during the depositional period of lower Zhujiang Formation.In general,the activity of the PY24 fault was intermittent.Its way to affect deposition was similar to the valve for fluid control.When the fault was weak in activity,like an opening valve,deposition continued in the sag,the thickness difference between hanging wall and footwall was small,and the distribution of facies belts was continuous and extensive.By contrast,when the fault was strong in activity,like a closed valve,most of sediments deposited in the accommodation space produced by the moving of footwall,the thickness difference between hanging wall and footwall was large,and facies change was drastic.The fault activity obviously blocked the progradation of coarse-grained sediments.So far most of studies have been focused on the affection of syndepositional concordant normal fault on sedimentation,but lack of the studies on synsedimentary antithetic normal fault.This study provided a case for syndepositional antithetic normal fault and its affect on sedimentation.