The effect of the polyfractional micromarble introduction on the change in the physical and mechanical characteristics of polymer composites based on low-viscosity epoxy binders has been studied. Evaluation of changes in compressive strength and tensile strength in bending of epoxy composites samples containing micromarble of three different fractions, depending on the degree of filling, was carried out. Using the method of least squares, mathematical dependences of the epoxy composites strength characteristics on the type of used micromarble and the degree of filling have been obtained. The analysis of isolines and Gibbs-Rosebom triangular diagrams allowed to determine the composition of the polyfractional filler, the composites on the basis of which have the greatest strength characteristics. Polymer composite containing a mixture of micromarble of different fractions in the amount of 80 % of the maximum filling level and having an increased compressive strength (up to 40 %) and close to the limit tensile strength during bending (decrease by no more than 10 %) compared to the unfilled composition epoxy polymer was obtained. The mechanical properties and the high filling degree of the obtained composite indicate the possibility of using micromarble as an effective filler for epoxy polymers, which is also confirmed by the achieved substantial economic effect.