Protein phosphorylation, a type of post-translational modification (PTM), has been identified in the addiction process. However, its role in social hierarchy remains poorly understood. In this study, we used the tube test to classify rats as dominants or subordinates. In the CPP paradigm, subordinates exhibited a higher susceptibility to addiction. Quantitative phosphoproteomic analysis revealed distinct phosphoproteomic profiles in the Nucleus Accumbens between these groups.