This paper proposes a novel transformerless single-stage single-phase three-level buck-boost voltage source inverter topology, which can realize power conversion in a wider input voltage range, and reduce the voltage stress of semiconductor devices and the current ripple of inductors. Compared with the conventional two-level buck-boost inverter, the voltage stress of switch devices in proposed topology would be reduced to half of the conventional buck-boost voltage source inverter. Since the current ripple of the inductor of the three-level topology is smaller, the inductor inductance can be further reduced. The simulation results verify the characteristic of proposed topology.