SiC power devices have higher blocking voltage, lower on-resistance, and higher operating temperature than Si-based devices, which can be widely used in electric vehicles, rail transit, and high-voltage power transmission. However, the more severe application environments put higher demands on their reliability. In this paper, 1.2 kV/20 A SiC Schottky Barrier Diodes (SBDs) were evaluated after subjected to a series of reliability tests, including high-temperature storage (HTS), low-temperature storage (LTS), high-temperature reverse bias (HTRB) and high voltage, high humidity, high temperature reverse biased (HV-H3TRB) test. All devices passed the HTS, LTS and HTRB tests, but only 80 % of the devices passed the HV-H3TRB, which was mainly caused by pre-breakdown before 1200 V. Failure analysis showed that the breakdown point was located at the edge of the termination with cracks and delamination of the passivation layer were observed. Of 80 % of the failed devices after HV- H3TRB, almost all showed failure mode of passivation layer damage. With the root cause, the failure mechanism has been identified. This indicates that the passivation layer plays a critical role to determine the reliability of a SiC SBD device.