Abstract: Based on the theory of turbulent kinematic flows, a simple approach to predict the diameter of jet-grouted column is proposed. Considering the process of jet grouting, the diameter of the jet-grouted columns is related to in-situ properties of soil and the jetting parameters adopted during construction. Since the fluid with high speed is jetted out from a nozzle to erode the soil during jet grouting, and there exists an erosion distance produced in the soil, the diameter can be estimated from this erosion distance. Through the analysis of free jet from a round nozzle and soil erosion, the erosion distance is obtained. Thus, the relationship among column diameter, jet parameters and soil properties can be established. Moreover, comparison between the predicted results and the data from literatures are also presented, and the results are classified according to the different soil types, which suggests that the proposed method is applicable for most soil types.