Abstract: The hydro-conversion properties and product distribution of vacuum residue mixed with coal tar were tested by ebullated bed. The spot test and instability parameter test were used to investigate the stability of the mixed oil before and after hydrocracking. The results indicate that the compatibility of vacuum residue is better than the mixed oil before hydrocracking. However, the stability of the hydrotreated blending oil is improved significantly, while the hydrotreated vacuum residue is the opposite. After hydrocracking of the mixed oil with a ratio of 7:3(residue to coal tar), the yield of distillate less than 500 ℃ increases and the coke yield decreases clearly.