Passivity theory provides a promising approach to guarantee microgrid system stability. If all converters in the system can be made passive, prevention of electrical resonance can be achieved. To that end, a passivity-oriented discrete-time voltage controller for grid-forming inverters is proposed in this -paper. Compared with existing methods, the approach ensures not only -superior reference tracking performance and load disturbance rejection capability, but also provides passive output impedance, and therefore, guaranteed stable inverter operation under weak grid condition. A comparison study is carried out and the proposed controller design method is validated by hardware-in-the-loop (HIL) experiments.