The calculation of local resistance of gas-liquid two-phase flow through an orifice is a problem pending solution in engineering design.A new model has been developed to solve the problem. The calculation on which the model is based has been verified by tests carried out on an air-water two-phase flow test-bed and is proved to be in good agreement with the experimental results. By comparing the value of the calculation with the data obtained from experiments of steam-water system, the authors found that, on the whole, this model fits in with the system of steam-water mixture. Therefore the model proposed covers a rather wide range of application and its calculation accuracy can meet the general requirement of engineering design.