Abstract: The grain size and clay composition and distribution of 161 samples taken from surface sediments in the Tangshan Harbor, Bohai Bay were analyzed to explore the provenance and the controlling factors. Results show that the average grain size (Mz) of the surface sediments was from 1.4 ～ 7.7 Φ, and mainly consists of silty sand, sandy silt, and a small amount of sand and clay. According to the characteristics of grain size parameters and end-member modelling analysis, the sediments can be divided into three zones and four end-members (EM1 to EM4). The northeastern part of the area is dominated by EM3 (sand and silty sand), with poor sorting, positive skew, and strong dynamics of depositional environments. The central Caofeidian Deep Trough area is dominated by EM4 (sandy silt and silty sand), with poor sorting, positive skew, and strong dynamics of depositional environments. The southern part and the Tangshan Harbor area is dominated by EM1 and EM2 (silt), with moderate-poor sorting and weak depositional dynamics. The clay minerals are relatively high in illite (72%) and smectite (12%), followed by chlorite (8%) and kaolinite (8%). The provenance analysis shows that the source of surface sediments in Tangshan Harbor is mainly the mixed detrital materials from Yellow River and Haihe River, while the northeastern part of the study area and the Caofeidian Deep Trough may have some coarse-grained materials from the ancient Luanhe Delta. The Bohai Sea circulation and tidal currents control the transport of fine-grained sediments mainly to the south and near Tangshan Harbor, while coarse-grained materials are transported and deposited to the northeastern and central Caofeidian area.