Abstract: In this paper, the path of rising buoyant plumes in neutral condition has. been analysed carefully on the basis of the data got from the observation in our country. It has been found that the plume rise height varies with distances. according to the power law, but there exist systematic departures from the 2/3 power law, which are cosistent with the non-linear relation between plume radius and plume heights. These facts as well as some results from the experiments abroad indicate that the accumulative effect of ambient turbulence on plume rise can not be neglected. Thus, a model including the joint effect of ambient and self-genarating turbulence is developed. A corresponding equation of mean path of buoyant plume has been deduced, and the observed facts can be explained satisfactorily. The model also shows that the entrainment velocity, in addition to depending on the shear velocity and the ambient turbulent intensity, is also the function of the effective plume radius. Thus it is more reasonable physically, and the plume rise formula deduced from the model is obviously better in agreement with those observation data than that without consideration of accumulative effect of the ambient turbulence.