Graphene oxide (GO) is a promising solid lubricant used as a protective coating to reduce friction, while a detailed atomic scale understanding about its tribological behavior is required. In this study, ReaxFF reactive molecular dynamics simulations are used to explore the friction and wear mechanisms of GO. At low load, the structure of GO can be tailored via the tribochemical induced conversion from graphene oxide to graphene (GO-to-Gr), achieving low friction during the sliding process. The effects of multiple sliding and system temperature on the GO-to-Gr conversion are considered. At high load, wear of GO at the nanoscale is characterized by the emergence of the C-C bond and C-O bond breaking, both of which are related to the transformation from the epoxide groups to the ether groups. Furthermore, we show that decreasing the concentration of epoxide groups is a feasible method to enhance wear resistance of GO.