Abstract: Visbreaking and hydrogen donor visbreaking of Venezuelan atmospheric residue were evaluated in an autoclave. The results show that hydrogen donor employ in visbreaking process is able to inhibit gas production, coke formation and asphaltene formation of residua in the thermal conversion process. To be specific, gas and coke yield in hydrogen donor visbreaking are less than that in visbreaking by 0.5%~1.2% and 0.02%~0.98% respectively, and asphaltene content of its residual oils is less than that of visbreaking by 0.6%~1.3%. With the reaction time increasing from 5 to 20 min at 425℃, the total and net viscosity reduction rate of hydrogen donor visbreaking process varies in 46.1%~54.8% and 10.2%~33.0%, respectively. The optimum reaction condition for hydrogen donor visbreaking process is obtained at 425℃ for 5 min. Under this condition, the properties of hydrogen donor visbroken oil are as follows: the spot test rates NO. 1 according to reference spot description in ASTM D4740, the kinematic viscosity measured at 50℃ is 185.5 mm²/s and the net viscosity reduction rate is 26.4%, which meet the basic requirements of transportation.