The performance of concrete materials deteriorates under load fluctuation and long-term erosion from the external environment, leading to damage. In order to solve the problems of concrete materials needing repair, poor working performance and the low mechanical strength of ordinary concrete repair materials, this paper explores a series of experimental studies on the preparation of ultra-high performance concrete repair materials and solves the two technical problems of the low early strength and poor fluidity of ultra-high-performance concrete. The effects of different steel fibers and dosages of early strength agents on the working properties, mechanical properties and microstructure of fast-hardening UHPC are discussed. Finally, the mix ratio of fast-hardening UHPC with a 2 h compressive strength of up to 47 MPa and fluidity of up to 300 mm is obtained through the test, which is in line with practical applications in engineering and provides a reference for the design and analysis of fast-hardening UHPC repair materials.