Abstract: A new version of one-equation turbulence model for predicting the incompressible,transitional flow over a flat plate is developed.Based on an analysis of the existing one-equation models and some physical features of the transitional flow,both the eddy viscosity and turbulence length scale in the turbulence kinetic energy equation are modified in order to bring the low Reynolds number effect into the new model.The capability of this model for predicting the transitional flow is demonstrated by an extensive numerical testing for flat plate flow under free stream turbulence intensity ranging from 0 03 to 8 percent.Both the start and length of the transition are correctly predicted.Comparison of the calcutated results of both the mean and fluctuating flow properties with experimental data indicates the agreement between them is very good.