Microfossils,pollen,Rb/Sr,Ti,magnetic susceptibility are utilized to understand environmental changes and human activities in the Zhangjiagang area since Tang Dynasty.During the early period of Tang Dynasty,there were marine diatoms,foraminifera,fish bones, water fern spores,etc.,combined with the characteristics of lithology,indicating that was a low-energy or hydrostatic fluvial depositional environment which was connected with the sea.Pollen,Rb/Sr,Ti analysis combined with the relevant historical documents indicated that climate was warm and wet in the Tang Dynasty,but up to the Song Dynasty, the climate changed to warm and cool.Pollen and magnetic susceptibility proxies suggest the site and the surrounding area suffered from human activity with more and more intensity.Climate change and human activities lead to the blockage of the ancient river G13 in the study area,i.e.the channel that connected to the sea was blocked.In addition, according to historical records,the north part of Zhangjiagang area quickly became land after the Southern Song Dynasty,which lead to the south coastline of Yangtze River eastward-moving,so Huangsipu port gradually lost its geographical advantage,which resulted in the decline of the ancient Huangsipu port.