Abstract: The theoretical model of a new-type turbine flowmeter is proposed based on the theorem of moment of momentum and the boundary layer theory of fluids, for analyzing the influence of the rotor's geometry on the flowmeter's metrological performance. The meter factor of a DN50 turbine flowmeter is calculated with the theoretical model and by using a standard volume tube. The effectiveness of the model is verified as it is shown that the calculated results are in a good agreement with the experiment results with an error in the range of ±3.5%, and the model provides a theoretical basis for the meter's optimization design.