Abstract: The k-ε turbulence model is used to establish a mathematical model for round negative buoyant vertical jets in flow ing environment. The model and the method are verified with the comparison between the calculated results and experimental data Streamlines and density contours in different section are given. It is also found that there is a low density region behind the inlet and the jets branch off after impinging the boundary and the density near the side is higher than which in the middle of the channel.