Grid-tied T-type inverters are widely used in photovoltaic, electric vehicle charging piles, and other grid-tied applications. However, the transistor fault seriously harms the reliability of the inverter. This paper proposed a simple and novel open-circuit fault diagnosis method for the grid-tied T-type inverter based only on the three-phase currents. At first, the Hausdorff distances among the three-phase normalized current accumulations are obtained to perform the fault detection. The process is tolerant of inverter transient conditions. Then, the fundamental frequency values of the three-phase currents are calculated to locate the faulty phase. At last, the faulty transistor is located by some intermediate conditions. In particular, the method is suitable for modulation index regulation. Experiments verify the effectiveness of the proposed method.