The composition of a heavy tar can still be divided into two fractions, the light organic components (LC) and heavy organic components (HC). The HC is hard to be processed into liquid fuel due to its high viscosity and coke formation tendency. In this work, the pyrolysis of HC is tested for improving the yield of LC product from HC pyrolysis with a microwave reactor. It is found that the existence of LC in heavy tar can promote the conversion of HC to LC product. As potential H donors, the effect of Anthracene (ANT) and 9,10-hydrogenated anthracene (HAN) in LC on HC pyrolysis are particularly evaluated. The improved yield of LC product from HC pyrolysis with LC is attributed to the hydrogenated aromatics in LC.