GB/T 2423.27-2020 "Environmental Testing—Part 2: Test Methods—Test Methods and Guidance: Combined Temperature/Low Air Pressure or Temperature/Humidity/Low Air Pressure Tests" is identical to the international standard. It integrates and replaces three previous versions of standards and is applicable to the complex environmental adaptability testing of electrical and electronic products and components. It specifies two types of combined test methods: temperature/low air pressure and temperature/humidity/low air pressure, and defines the control ranges for temperature (-55°C to 155°C), air pressure (5 kPa to 70 kPa), and humidity (10% RH to 95% RH), as well as the rate-of-change requirements for temperature (≤1 K/min) and air pressure (≤15 kPa/min). The distinction between heat-dissipating and non-heat-dissipating samples has been removed, and an appendix with test guidance has been added to standardize the entire process, including preconditioning, condition application, maintenance, and recovery. It is used to simulate complex environments such as high-altitude and aviation conditions, evaluate product performance stability, and provide a unified basis for product design verification and quality qualification.