The quantitative geochemical model for origin of Li-F granites of the Orlovsky deposit (Eastern Tansbaikal) has been developed. Mineral-forming media composition (rock-forming elements, Li, Rb, Cs, Ta, Nb, W, Sr, Zr, Ba, F) for the different evolution stages of Orlovka granite massif was estimated on the basis of the mass balance calculation taking into account rock composition, spatial and volumeric relationships. An effective integral partition coefficients of Fe, Mn, K, Na, Li, Rb, Cs, Ta, Nb, W, Sr, Zr, Ba, F and partition coefficients between magma and potassic feldspar, mica, quartz and Zr were determined. These data conform with the results, obtained by the conventional method of investigation.