In order to master the deformation regularity of earth-rock cofferdam with pure concrete linked water cut-off pile,the monitoring data of earth-rock cofferdam with pure concrete linked water cut-off pile in different position of different dewatering stage for different monitoring items was analyzed and summarized.The results showed that:the deformation of cofferdam was remarkable large during the first time dewatering,but the increase trend of cofferdam deformation was slowed down obviously during the second time dewatering after refilling sea water into dock,refilling riprap at the foot of cofferdam,widening and strengthening cofferdam;the deformation of the cofferdam in the middle was largest,near landing position was slightly large and the landing position kept stable during entirely dewatering period;the increase trend of monitoring data from different monitoring items in the same position was consistent.After analyzing,the rate of dewatering 400~500 mm/d was determined as the most reasonable finally which can ensure the safety of cofferdam and to some extent speed up the dewatering making sure the construction time.