Abstract: This test is one of the projects specified in the commissioning program for Fangjiashan nuclear power units, which is mainly to verify that when the water is supplied by the auxiliary feed water system with one broken feedwater line, the total flow from the break shall not be more than 250 m³/h, and the feed water flow to each of two intact steam generator（SG） shall not be below 45 m³/h. The difficulty lies in the fact that there will be no break in the test, and no flow data can be measured directly. A model is established to analyze the operation point of the auxiliary feedwater pump during the breakup accident, and fit the unknown parameters in the model with the data from normal tests. And then we can calculate the water supply flows to the breakup and normal lines with all the operation point data. Analysis shows that the water supply data meets the requirements of the acceptance criteria.