Purpose: Study of strength and deformation properties of basalt broken stone ballast depending on its grain composition, the properties are necessary for further assessment of bearing capacity and deformability of railway track ballast layer. Methods: Determination of mechanical properties of broken stone ballast from basalt rock was carried out in a triaxial compression chamber which intense state close to real operating conditions was simulated. In the trial process, the dependences of axial and volumetric deformations from tension deviator were being determined. The methods of trial result statistical processing and regression analysis were used in the work. Results: According to laboratory test result statistical processing, the key characteristics of broken stone ballast strength as well as deformation modulus and Poisson’s ratio depending on the ballast grain composition were determined. Practical importance: The study results make it possible to elaborate recommendations regarding broken stone ballast grain composition, the ballast is from the basalt used in the areas of especially heavy traffic of trains.