A current-source sine-wave voltage inverter for converting a direct current (DC) voltage to an alternating (AC) voltage includes a DC source for providing a DC voltage, a current source circuit having a primary side inductance of a transformer, a clamping circuit, an inverting circuit, and a control and driving circuit. The clamping circuit includes a first switch cascaded with a first diode, a second diode cascaded with a second switch, a first capacitor connected between an anode of the first diode and a cathode of the second diode, a secondary side inductance of the transformer cascaded with a third diode, the secondary side inductance of the transformer and the third diode connected to two ends of the DC source, and a cathode of the third diode connected to an anode of the DC source. The present invention also provides a fuel cell system.