Abstract: Based on the research concept of catalytic depolymerization,using the Gary-King retort,the effect of catalyst and accessory ingredient in the catalytic depolymerization of Inner Mongolia lignite were investigated by adding catalyst with accessory ingredient,only adding catalyst and only adding accessory ingredient. The results showed that the addi- tion of catalyst or accessory ingredient intervened the coal pyrolysis and products yield of gases or liquid phases. When only adding accessory ingredient,the fracture degree of the hydroxyl and fat side chains in the coal is deepened;when only adding catalyst,the fracture,dehydrogenation and aromatization of the bridge bond in coal are promoted;and when adding catalyst with the accessory ingredient,the superposition results of only adding catalyst and only adding accesso- ry ingredient are reflected in all aspects,but the increase in tar yield reflects a certain degree of synergistic effect. Adding catalyst with the accessory ingredient is more beneficial for the formation of tar,which increased from 5. 84%of raw coal tar yield to 7. 28% .