A functional copolymer viscosity reducer based on molecular dynamics simulations was syntlfesized using monomers of mixed ester, 4-vinylpyridine, and styrene. The possible structure and number of hydrogen bonds within the complex structure of heavy oil were simulated and analyzed after the copolymer was added. Results showed that the number of hydrogen bonds in asphaltene in the simulation structure decreased from 36 to 28 per unit volume with the addition of the copolymer. The original plane overlap structure of asphaltene was damaged as soon as interactions occurred between the asphaltene and copolymer molecule. The potential energy of the system was higher with the addition of the copolymer, while the non-bond energy difference of the two systems was not obvious. The stereohindrance effect of the copolymer viscosity reducer molecules either broke or improved the interlocking structures of the asphaltene, helping to decrease the viscosity of the heavy oil.