AbstractA numerical method for calculation of the weight‐fraction distribution resulting from random crosslinking of polydisperse primary chains is suggested. The method is based on the numerical inverse Laplace transform of the weight‐fraction generating function given by the theory of branching processes. The applicability of the method was demonstrated using the Schulz‐Zimm type distribution of primary chains. A good agreement was obtained by comparing the results with those following from the kinetic theory of crosslinking for the most probable distribution of primary chains at low degrees of crossli