In this paper, systematic supercritical carbonation tests of steel-polypropylene hybrid fiber reinforced concrete (SPFRC) were carried out to evaluate the performance of SPFRC under supercritical condition . The effects of the length-diameter ratio of steel fiber , volume fraction of steel fiber, and polypropylene fiber on the carbonation depth and compressive strength of concrete under supercritical condition were studied. A one-dimensional mathematical model for the physical-chemical coupling process of supercritical carbonation of cement-based materials was established. The relational model between the equivalent porosity and the compressive strength of fully carbonated SPFRC was also proposed. Results indicate that whether the addition of steel fibers or polypropylene fibers or the inclusion of fibers can accelerate the carbonation process by the increase of porosity. The carbonation depths of SPFRC increase with the increase of the addition of steel fibers and polypropylene fibers. The compressive strength after carbonation is significantly increased. The maximum relative compressive strength was obtained when the volume fraction of steel fibers and polypropylene fibers were 1.5% and 0.0% and the length-diameter ratio of steel fiber was 60, respectively. Furthermore, a mathematical model was proposed to evaluate the equivalent initial porosity of SPFRC. • The supercritical carbonation of SPFRC were first studied experimentally and numerically. • The performance of SPFRC under supercritical condition was evaluated. • The effects of fiber types and contents on the carbonation depth of SPFRC were studied. • A relational model between the equivalent porosity and the compressive strength of fully carbonated SPFRC was proposed.