To determine the times of travel within a 170.6 km long reach in the upper Yellow River, we carried out a dye experiment in May 2017. 48.75 kg of dye was poured simultaneously at 39 points on a floating bridge. Water samples at eight sites were collected at left bank flow, center flow, and right bank flow considering both the traffic convenience and the safety production. A Fluorometer 10-005 was used to measure the dye concentration in the water samples. A three-parameter lognormal distribution equation, where the logarithm is to the base e, was used to fit the observed time concentration data to establish the time-concentration response curve and to establish the probability density function. For a conservative tracer, the time concentration curve was generated by multiplying the fitted probability density function and its coefficient. The travel times of different parts of the dye plume for the seven sampling sites and mean velocities and longitudinal dispersion rates for five sub reaches were calculated. The mean velocities of centroid of dye plume ranged from 0.49 m $s^{-1}$ to 0.69 m $s^{-1}$ and the dispersion rates range from 0.13 m $s^{-1}$ to 0.37 m $s^{-1}$ for the discharge of 233 $m^3$ $s^{-1}$ measured at the Baotou hydrometric station. Several empirical relations are given for attenuation of the peak probability density, passage time, travel times of leading-edge, travel times of centroid and travel times of trailing edge of the dye plume in the upper Yellow River, Baotou, Inner Mongolia, China.\\