In the 1 000 km long tidal reach of the Yangtze River, semi-diurnal tide wave goes against the stream from the estuary arrives upstream of Anqing, Anhui province. The reach is divided into the with-tide area and without-tide area by the tidal mark, and the current characteristics change area is divided by the tidal current mark.Therefore, the location of them is significant for the economic development, agriculture planning, ecological environment,navigation, waterway engineering, harbor construction, navigation safety and scientific development, etc. of the area. Based on the spot investigation data, and by the numerical simulation and harmonic analysis, it is concluded that the tidal mark of the Yangtze River is located between Anqing and Nanjing, the tidal current mark is located between Zhenjiang and Jiangxinsha. The new idea is quite different from the tradition idea, i.e., in general regard,the tidal mark of the Yangtze River is located between Tongling and Wuhu of Anhui province, and the tidal current mark is located downstream Jiangyin.