There is not any hydrometric station in the convergent section of Dam River and Tuotuo River, then the Dam river as new main source of the Changjiang River has only hydrometric station in a tribulary of the Buqu River and the Gaerqu River。the other tributary does not establish anyone．Therefore，hydrological data is gaps before now，data of the Dam River is not complete too，it is difficult tO estiillale its hydrological characteristic．

    This paper first provides data of the Dam River and Tuotuo River based on field measure，fills gaps and analyses the hydrological characteristics．The data shown that the Dam River and TuoOtuo River Irove difference in the type and structure of river bed，discharge of the I)aIll River is 196.1 8m3／s．Ihe Tuotuo River is only 29.90m³／s，both of them show the relationship between main river and tributary．The discharge of the Tongtian River is 226.08m³／s，it is so rich，this is as a result of recharge from rainwater，swamp water，mehwater of ice alld snow．and spring water etc in the source region of the Changjiang River．