Abstract Throughout the entire life cycle of electrical and electronic products, waterproof performance in outdoor or humid environments is a critical indicator determining product reliability and safety. This paper takes the LISUN JL-UL UL Rain Test Apparatus as the research object, and based on international authoritative standards such as UL 1598 and UL 60598, systematically analyzes the design principles, core technical parameters, and testing procedures of this apparatus. It focuses on expounding its specific applications in rain performance testing of electrical and electronic products, lamps, electrical cabinets, and electrical components. A test parameter comparison table is constructed to intuitively present the testing conditions for different products, and practical test cases are used to verify the practicability of the apparatus. The research shows that the LISUN JL-UL UL Rain Test Apparatus can accurately simulate rain climate conditions of different intensities. By dete...