In this paper, the damage mode and non-destructive testing technology of high density polyethylene (HDPE) as the liner material of type IV high pressure hydrogen storage cylinder are reviewed. The possible damage of HDPE materials in high pressure hydrogen environment mainly includes hydrogen permeation, material aging and stress damage. Summarizing the academic research, it is found that temperature and crystallinity have a significant effect on hydrogen permeability, while aging and stress damage are closely related to environmental factors and mechanical behavior of materials. The article also discusses a variety of non-destructive testing techniques, such as acoustic emission monitoring, infrared thermal imaging and ultrasonic testing, which are essential for assessing the safety and durability of gas cylinders. Future research needs to comprehensively consider these damage modes and optimize non-destructive testing techniques to improve the overall performance of cylinders.