Abstract: The research about the steam-water separation mechanism is very significant, and it is essential to obtain the initial parameters of the drops, as it is the basis of the whole steam-water separation research work. The film drop is one of the important sources of the entrainments. A film drops production model was built up with reasonable assumptions, and the correctness of this model was testified with experiment results. This work mainly researched the phenomenon of the film drops produced by the bubble bursting at a free water surface in the steam generator. The film drops production model was used to estimate the initial information of film drops produced in the steam generator of the Ling’ao Nuclear Power Station in unit time, obtaining the distribution curve of these parameters in the direction of the radius of the steam generator, including the number, diameter, velocity and initial position.