Using pre-absorbent low active slag as internal curing material instead of fine aggregate, the autogenous shrinkage and resistivity variation of low active slag internal curing mortar were studied, and the relationship between them was revealed. The results show that with increase of low active slag content, the early strength of mortar decreases greatly, with the extension of age, the strength reduction in the middle and late stages of mortar is smaller than that in the early stage. It is suggested that the appropriate content of low-activity slag is 15%-25% of the fine aggregate quality. The internal curing of low active slag has obvious influence on the resistivity development of mortar. Before setting hardening, the resistivity of mortar increases with the increase of low active slag content. After it, the slurry resistivity decreases with the increase of low active slag content. The internal curing of low active slag can effectively inhibit the autogenous shrinkage at various stages of the slurry, especially in the rapid shrinkage stage and transient expansion stage. At the same time, the resistivity after 36 h has a good correlation with autogenous shrinkage, and the change of autogenous shrinkage can be predicted by the development trend of resistivity.