Abstract: A full-life low-carbon cement mortar may be designed by incorporating waste ceramic, stainless steel fibers, and penetrating crystalline admixture. As a key material in construction engineering, the mechanical properties of mortar are core evaluation indicators. Compared with studies on the effects of penetrating crystalline admixture on the mechanical properties of ordinary cement mortar, there are few studies on its influence on the mechanical properties of waste ceramic composite steel fiber cement mortar. Therefore, this paper explores the influence laws and mechanisms of the penetrating crystalline admixture content on the workability, setting time, mechanical properties, and electrical properties of steel fiber reinforced mortar with waste ceramic (SFMWC) and established mechanical-electrical fitting models. The research results show that with the increase in the content of penetrating crystalline admixture, the flowability and setting time of SFMWC both decrease: an appropriate content of penetrating crystalline admixture can improve the flexural strength, compressive strength, splitting tensile strength, fracture toughness, compressive toughness, and splitting tensile toughness of SFMWC, among which the compressive toughness and splitting tensile toughness are significantly improved, reaching 45.9% and 105.0%, respectively. Mechanical-electrical fitting shows that there is a significant correlation between the mechanical properties and electrical properties of SFMWC, and the correlation between AC electrical resistivity and flexural strength is the most significant. Microscopic analysis shows that penetrating crystalline admixture can optimize the internal structure of SFMWC, reduce the crack width of the interfacial transition zone, decrease the total porosity, and optimize the pore structure, thereby improving the mechanical properties of SFMWC.