Abstract: In order to evaluate the insulation state of cables under very low frequency electric field detection, the electric field threshold of space charge accumulation in very low frequency detection was analyzed by measuring the space charge response of cross-linked polyethylene with different aging states under sinusoidal fields of 50, 0.1 and 0.01Hz. The insulation sate evaluation method was discussed with their physical properties and breakdown field. The results show that the specimen has no threshold inflection point for the space charge accumulation under 50Hz electric field, but a threshold field is observed under 0.1 and 0.01Hz electric fields, with a value of about 10~15kV/mm. The mean bulk charge density at 180° phase and the mean phase charge density increases significantly when the very low frequency field exceeds the threshold field, which was mainly related to the duration of the effective electric field under very low frequency field. The mean phase charge density of aged samples decreases significantly under 0.01Hz electric field, and the space charge on the surface of sample change from heterpolarity to homopolarity. The continuous distribution area is much larger than that of unaged samples. This may be related to the decrease of deep traps and to an increase of shallow traps, both of which increase the charge migration rate and inhibit the accumulation of space charges. As the aging degree deepens, the mean phase charge density and breakdown field strength of aged samples under 0.01Hz electric field decrease obviously, which indicates that the space charge under very low frequency fields can characterize the aging states of samples. The accumulation, polarization and distribution of the insulationspace charge should be integrated when the space charge characteristics of very low frequency field are used to evaluate state, providing a theoretical basis for the evaluation of cable insulation state under very low frequency electric field.