A three-dimensional hydrodynamic mathematical model and physical experiment of the vertical jet in circular pipe with negative buoyant effect was conducted in still water, and the calculated non-dimensional vertical velocity of the model was in good agreement with that of the experiment. Then, the hydrodynamic characteristics of the negative buoyant jet was analyzed accordingly. The results showed that with the increase of the initial jet velocity and the decrease of the initial jet density and the nozzle exit diameter, the maximum rising height and the steady height increased; however, the initial jet velocity and initial jet density had insignificant influence on the time and rate of the vertical velocity decay at the central line. With the increase of the initial jet density, the vertical velocity decay at the central line tended to arrive late and the decay rate increased; whereas it happened early and the rate decreased at the moment of both maximum rising height and steady height with the increase of the nozzle exit diameter for the scenario of steady height. Based on the findings, the density Froude number was used to obtain the dimensionless linear relationship formulas for predicting the maximum rising height and the steady height respectively. The ratio of the maximum rising height to the steady height was close to the constant of 1.52, which was roughly independent of the density Froude number. The research aims to shed some light on the design and engineering application of the vertical jet with negative buoyant effect in still water.