Abstract: In order to facilitate the calculation and utilization of the equivalent rectangular stress-strain diagram coefficients and plastic damage parameter of reactive powder concrete (RPC), a theoretical study on the calculation model of RPC stress-strain curve coefficients and plastic damage parameter has been conducted. By nondimensionalizing the existing calculation methods, 4 indefinite integrals that determine the calculation model are deduced. A practical stress-strain relationship was calculated, and the results obtained were analyzed; and the presumptive calculation of internal forces and moments on the cross section of a cantilever beam in the non-limit state was demonstrated. A curve fitting method is proposed for the case where the stress-strain relation contains non-integer rational fractions, and the effects of fitting times, fitting intervals and fitting function types on fitting accuracy and stability were studied. The stress-strain curve coefficients and damage parameter value model of 4 typical RPC constitutive models under the same material were compared, and the result shows that: the value models obtained from fitting curves and obtained from other original curves have high similarity on the curve shape, which proves the accuracy and reliability of the curve fitting method. Finally, a dimensionless calculation model for RPC compressive stress-strain curve coefficients and plastic damage parameter is developed.