Abstract: High-voltage and high-power devices are currently widely used in various large-capacity power conversion and control equipment, facing complex electrical-magnetic-thermal-mechanical stress during operation, characterized by high power density and complex operating conditions. Conducting characteristic tests of high-voltage high-power devices is beneficial for accurately assessing the reliability of power devices and guiding the optimization design of converters. Focusing on the quasi-online testing method utilizing double pulses, this paper comprehensively reviews the application and current development status of quasi-online testing in areas such as junction temperature extraction, aging characterization, safety boundary delineation, and electromagnetic field mapping. Then, it categorizes and examines the strengths, limitations, and applicability of various characteristic characterization methodologies. Furthermore, it further explores real-time status monitoring and life evaluation methods for power devices under online operating conditions. Additionally, the targeting third-generation silicon carbide semiconductor device, a new evaluation method based on electroluminescence principles, is proposed, providing guidance and reference for the subsequent reliability evaluation of high-voltage high-power devices.