An investigation has been made of the kinetics of thermochemical conversions of the concentrate of catalytic cracking heavy gas oil under isothermal conditions in the 360-400 degrees C temperature range. A kinetic model of this process was obtained, and the rate constants and temperature coefficients of individual stages of thermochemical conversions of the group components of the pitch were determined. An equation is proposed which links the content of an optically anisotropic phase, determined by the optical method, with the group composition of the mesophase pitch.