The commissioned deep water berths near the entrance of Tianjin Port have been in the alternation of siltation and dredging since their coming into use in November, 2008. The monthly mean back silting intensity in front of the docks is 1耀1.5 m, which is far more than the theoretical intensity. This paper analyzes the reasons for heavy siltation near oil docks and in harbor based on the sediment source of Tianjin Port,the normal siltation, the recent depth contrast, the dredging project and so on, which is mainly caused by dredging project. And the standpoint that siltation can be decreased by enlarging area of deep water berths and increasing partial channel depth is put forward based on that working with suction dredger in the channel has the largest impact and the prediction that the normal annual average siltation thickness in smaller than 0.7 m.