The upgrading of heavy oil from Karamay using supercritical methanol (SC-MeOH) as a solvent was studied in a batch reaction. Through orthogonal experiments, the effects of the temperature, mass ratio of methanol to oil, reaction time, and agitation speed were investigated. The optimal reaction conditions, depending on the boiling range of light products such as maltenes and the yields of byproducts such as asphaltenes, were as follows: reaction temperature of 350 degrees C, reaction time of 60 min, stirring agitation of 900 rpm, and mass ratio of methanol to oil of 1:1. A simultaneous increase agitation speed would significantly reduce the condensation behavior. Analysis of the simulated distillation of maltenes indicated that the components with boiling points lower than 380 degrees C increased from 19 wt % in the raw material to 38 wt % in the maltenes products. The viscosity of light products decreased to 24.1 mPa.s. The FTIR of asphaltene results showed that the temperature has contradictory influence on upgrading of heavy oils. With increasing temperature, the degree of aromatic ring condensation increases and the lengths of aliphatic side chains decrease. High temperature can promote the breakage of alkyl side chains and condensation of aromatic rings. The TG-FTIR spectrum proves that SC-MeOH can participant in the reaction as a reactant. However, heteroatom O was introduced into the maltene molecules. All these results proved that SC-MeOH is an excellent solvent for oil pyrolysis. However, the quantity of light products should be improved, the secondary generation of asphaltenes removal needs to be restrained, and heteroatoms need more detailed research.