The co-pyrolysis characteristics of low-rank coal (SJC) and heavy oil (HS) were investigated using a thermogravimetric Fourier transform infrared analyzer and a vacuum tube-type furnace reactor. The structure and composition of the pyrolysis products were characterized through gas chromatography-mass spectroinetry, Fourier transform infrared spectrometry, and gas analysis. The coke yield decreased by 20%, and the gas and tar yields increased by 7.74 and 12.18%, respectively) after combining with HS. Meanwhile, the number of hydroxyl groups on the coke surface decreased, and the alkane and phenol contents of tar decreased by 7.89 and 8.10%, respectively. The aromatic substance,content increased by 21.60%. The HS was upgraded after the co-pyrolysis of SJC + HS. The HS did not affect the. precipitation temperature of each component in the pyrolysis gas. The CO2, CH4, and CnHm contents were augmented by about twice the original amount, whereas the CO and H-2 contents were diminished by 2.88 and 22.18%, respectively. The initial decomposition temperature of SJC + HS co-pyrolysis was greatly reduced. The cracking of the light component in the HS appeared in the first stage, but the maximum mass loss occurred in the second stage. Hydrogen donation and synergistic effects for the radicals produced by coal pyrolysis with the pyrolysis products of HS redistributed the co-pyrolysis products, increased the pyrolysis tar yield, and sharply reduced the CO and H-2 contents.