Abstract: According to the characteristic of delayed coking feedstock and the basic principle of Monte Carlo method, Monte Carlo simulation was used to characterize feedstock of delayed coking, vacuum residuum, with reference to molecule expression of structural oriented lumping. The results show that it can characterize feedstock on the basis of molecule, and the generated 1 000 molecules reflect characters of feedstock very well. This method is feasible for feedstock simulation of complex systems, and establishes a base of molecular model for delayed coking.