An improved high voltage boost Z-source inverter topology is proposed to improve voltage boost ability. Compared to the conventional Z-source inverter, it can produce very high voltage boost with a short shoot-through duty ratio, the voltage stress on Z-source capacitors and inverter-bridge is greatly reduced, and has inherent limitation to inrush current at startup. The addition of a input capacitor and an active switch allows the current in the Z source network to flow in the reverse direction, which adapts to a wide range of the load change. Theoretical analysis, the operation principle of the proposed topology and comparison with the conventional topology are explicitly described. Simulation and experimental results are presented to demonstrate the new features.