It is described the simple prediction of the flow and the noise characteristics of the sirocco fan. The prediction is based on the method of the potential flow condition, which is provided with the source and the circle vortex in axisymmetric flow condition. The turbulent noise is estimated by the transformation to the linear cylinder. The prediction is examined in relating to the influences of diameter that is checked with the experiments. The scale of the separation near the front shroud is slightly increased with the diameter. The pressure is gradually decreased and the variation of it is well agreed with the experiment. The turbulent noise level is relatively good agreed to the experimental result. The validity of the simple prediction was obtained to the fluid and noise characteristics.