Abstract: This paper simulates the mixing mechanics of submerged,multi-port diffusers used to discharge heated water from stream-electric power plants,and households into shallow receiving waters.The 3-dimensional turbulence modelling and the hybrid finite analytic method are used to predict the dilution behavior of near field for multiple jets in river.The predicted dilutions are good by comparision with available laboratory measureents.A empirical formula for temperaturs dilution in near fields for this kinds is given.It is very interesting that there are bifurcation and Coanda effect in this kind flow.