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The mobility and aggregation behavior of macromolecular lubricant oxidation products and their influences on the performance of base stock were probed by molecular dynamics (MD) simulation. The mean square displacement (MSD) of molecules was calculated to explore the mobility of molecules. The distribution appearance of lubricant oxidation products in models was acquired to explore the aggregation of molecules. The results show that the mobility of macromolecular oxidation products is lower than that of base stock. The MSD of macromolecular oxidation products reduces with an increasing macromolecular weight. Macromolecular oxidation products can also decrease the mobility of base stock. The interaction energy between the macromolecules and the base stock soars with the increase of macromolecular weight. Macromolecules with a larger molecular weight can affect more base stock molecules with stronger restriction, which leads to lower mobility of base stock molecules. There are aggregates formed among macromolecular oxidation products, and the molecules in aggregates are connected by hydrogen bonds. The quantity of hydrogen bonds in aggregates is related to temperature.