Abstract: To investigate the influence of water absorption rate on the electrical properties of low smoke zero halogen flame retardant polyolefin cable materials, the water absorption rate was regulated by adjusting the ratio of polar resin (EVA) to non-polar resin (mLDPE). The dielectric constant, dielectric loss tangent, capacitance, volume resistivity, and immersion breakdown strength under different water absorption rates were systematically measured, and the effect of irradiation crosslinking on breakdown performance was examined. Results showed that with the increase of water absorption rate, the immersed capacitance, dielectric constant, and dielectric loss tangent increased gradually first and then sharply, while the immersion breakdown strength decreased sharply initially and then more slowly. In a high-humidity environment, possible residual microcracks or free radical sites from irradiation combined with polar groups, leading to enhanced interface polarization and ionic conduction, a sharp rise in leakage current, and a continuous decrease in breakdown strength, eventually approaching the level of un-crosslinked materials. Under low water absorption conditions, the three-dimensional network structure formed by irradiation crosslinking restricted molecular chain movement and reduced internal voids, resulting in a higher and more slowly varying breakdown strength. This study provides a reference for predicting the electrical properties of cable materials based on water absorption rate and improving their long-term reliability.