Water environmental capacity is an important base for making the river pollution control, weakening the pollution source and realizing the water-function target. Analyses on the present situation of water quality in Suzhou reach of Tuohe River are conducted. The hydrological characteristics, the contamination characteristics and the water environment status were investigated. Combined with the design procedure of the water environment capacity, one-dimensional water quality model was selected to calculate and analyze the water environmental capacity of Tuohe River. The results showed that the water environmental capacity of BOD5 is 1231.16t/a, CODCr is 4289.73t/a and NH3-N is 377.3t/a. The current water quality of Tuohe River was good in general, most of the river’s sections have residual water environmental capacity and it is necessary to carry out total pollution reduction plans (especially for COD) in future with the population growth and socio-economic development.