Abstract: Due to the strong hygroscopicity of low-smoke halogen-free flame retardant polyolefin insulation, which seriously affects the long-term operational stability and safety of low-smoke halogen-free cable, influence of different types of resins, various flame retardants and irradiation cross-linking on water resistance of insulation materials was investigated using the gravimetric method. Results indicated that water absorption rate of the insulation material decreased as the content of ethylene vinyl acetate copolymer (EVA) decreased, and it also decreased with the increase in the proportion of metallocene linear low-density polyethylene (mLLDPE) and poly (ethylene-co-1-octene) (POE). Among flame retardants, magnesium hydroxide (MDH) raw powder exhibited a significantly higher water absorption rate than aluminum hydroxide (ATH) raw powder, whereas calcium carbonate (CaCO₃) raw powder demonstrated the lowest. Additionally, modified inorganic flame retardants showed a lower water absorption rate. Furthermore, as the irradiation dose gradually increased, the degree of cross-linking rose, leading to a progressive reduction in water absorption rate of the insulation material. The above research results could provide reference for the selection of cable materials, especially low-smoke halogen-free flame retardant insulating materials with humidity requirements.