Abstract: The empirical coefficient may be affected by slope, flow velocity, discharge and other factors. Compared with the velocities measured by salt tracer and discharge method, the empirical coefficients increased with the velocity enhance in lower sediment concentration flow, vary little when the sediment concentration was high enough, but the correlation between the velocity and coefficient was not good enough. The mean coefficients in different slopes were right interrelated strictly to the sediment concentration, so the sediment concentration is the main factor affecting the coefficient of tracer flow.