Calculations data of Gibbs energy of interaction reactions between wollastonite, light metals and the basic alloying elements of alloys on the basis of aluminium and magnesium are presented in the work. For reasons given the forecast of the most probable reactions is made. Interaction of aluminium and magnesium fluxes with a wollastonite surface is investigated by «diffusion pair» method and shown, what between them reactionary diffusion is developed. Aluminium react with wollastonit by the temperature more than 800 ^оC, during this Ca and Si reducing to elementary state and was generated compounds Al₂O₃, Ca₂Al(Al,Si)₂O₇, Ca₃Al₂O₆, CaAl₄O₇, CaAl₂Si₂. Magnesium intensive interaction with wollastonit by the temperature more than melting point, it`s generate compounds MgO, CaMgSi, Ca₂SiO₄. Assumptions about the mechanism of modifying structure of alloys on the basis of light metals by wollastonite are suggested and possibility of using needle wollastonite as filler of aluminium-matrix composite materials is shown.