[en] Method for analysing binary nuclear reaction in the four-body approximation in (2.2) channel, when both interacting ions dissociate into two clusters in considered. Formalism, based on 4-particle problem reduction to 3 particle one is developed for the reaction matrix element calculation. In this case the amplitude of the reaction investigated is expressed through the coherent sum of three-particle apmlitudes of direct and exchange processes taken outside the mass surface. Concrete expressions for calculating the matrix element are derived using the instrument of reduced widths. A brief description of a calculative program in which the considered method is numerically realized is given. 6 refs.; 4 figs