The invention relates to an anti-corrosion anti-cracking reinforcing agent composition for concrete, mortar, and net slurry used in injection (first-aid repair) engineering, and a preparation method thereof. The composition comprises the following components on a percentage basis: 2-50% of micro-expansive powder, 5-30% of reinforcing powder, 5-20% of anti-corrosion compacting agents, 10-20% of plasticizers, 1-6% of catalysts, and 10-60% of carriers. The composition of the invention prepares solid and liquid products by processes of melting refinement, polymerization, ball milling, jet milling, complex formulation, and the like, and thus meets construction process requirements of different first-aid repair endurance engineering.