In data center application, the bus converter not only needs to achieve high step-down gain but also keep a high efficiency when the dc bus changes voltage in a wide range. In this paper, a novel high step-down buck-boost converter based on tapped inductor with a wide input voltage range is presented. Due to the tapped inductor, the proposed possesses high step-down conversion capability. Moreover, when input voltage changes greatly, the duty cycle of the converter can be controlled to a suitable range and hence maintain a high efficiency. The theoretical analysis is verified by prototype with a wide input voltage (36-60V), 3.3V output voltage, and rated output current 10A.