AlGaN-based UVC LEDs have encountered a problem of low reverse Electro-Static Discharge (ESD) and low light efficiency due to the high Al composition in their epitaxial structure, which results in low reliability and lifetime degradation. In this study, a reverse diode (ESD device) was added to the device fabrication of the AlGaN-based flip-chip UVC LED to improve the negative ESD capability. By optimizing the design of the ESD protection diode and the N contact, the negative ESD capability can be significantly increased from −150V to −1800V, effectively solving the problem of weak ESD in AlGaN-based UVC LEDs. Additionally, the Light Output Power (LOP) and Wall-Plug Efficiency (WPE) can be increased by 10-18%.