The invention discloses a Buck terminal coupled inductor buck-boost conversion circuit and belongs to the DC non-isolated conversion technology, and the stable output voltage can be achieved in a wideinput voltage range. According to the invention, a coupled inductor, three power switch tubes and three freewheeling diodes are mainly used to achieve a buck-boost function, and the stable output voltage is ensured. In the present invention, the current in a Buck terminal coupled inductor operates in a discontinuous mode, the zero-current turn-on of two power switch tubes of a Buck terminal and the zero-current turn-off of two freewheeling diodes of the Buck terminal can be achieved, the problem of the reverse recovery of two diodes at the Buck terminal is eliminated, therefore, the soft switching function is realized, and the efficiency of the conversion circuit is improved. The current sharing control is not required, and even if the duty ratios of the two power switch tubes of the Buckterminal are slightly different, the uniform current of two inductor currents in the coupled inductor can be realized. The invention is suitable for applications such as wide input electric vehicles,fuel cells, photovoltaic power generation, wind power generation and other new energy supply systems.