In this study, a computational model based on similarity analysis is proposed to simulate the steam generation phenomena and the inflow pattern of Deionized water(DIW) of the multi-vessel steam generator. Similarity analysis is performed to reduce computation time of multi-vessel steam generator model. Multi-vessel with similarity analysis predicts the possible problems that can occur during the heater malfunction of a pressure vessel. Moreover, two different inflow types of DIW pipeline configurations are compared to find out the best uniform distribution of DIW to all pressure vessels. These results show that the heater malfunction causes the steam flows from normal operating pressure vessels to a malfunctioning pressure vessel. In addition, the results show that the cascade inflow type of DIW pipeline can uniformly supply DIW to all pressure vessels better than parallel inflow type of DIW pipeline.