In this paper, the hydrological characteristics of Heishui River in Sichuan Province were studied, with electrical conductance (EC) as the main indicator. A total of 10 sites were selected on the branch and main streams, and the EC determinations were made at low-flow and level-flow periods. The results showed that EC value was significantly different among test sites, but had no significant difference between the two sampling times. The t-test on the EC values of different sites at two sampling times also showed the similar pattern, indicating that the index EC could be helpful for distinguishing hydrological period and indexing river characteristics, and the contribution of branch stream to its neighboring main stream could be estimated by the EC. Using EC as a characteristic index of hydrological temporal-spatial changes could provide a convenient way for the further studies of catchment hydrology.