Polystyrene with pi-conjugated end groups (BPS) synthesized by reversible addition-fragmentation transfer polymerization was used to modify the surface of reduced graphene oxide (rGO) sheets through pi-pi stacking (BPS-rGO) in order to increase their hydrophobicity and dispersibility. The modification of rGO makes it possible for BPS-rGO to stabilize Pickering w/o (water-in-oil) emulsions of small droplets, in which toluene is taken as the continuous phase and distilled water as the dispersed phase. The effects of the BPS-rGO concentration and the water/oil ratio on the Pickering emulsions were investigated. The results indicate that increasing hydrophobicity of BPS-rGO was favorable to forming stable w/o emulsions and the emulsion stability was increased with the increase in the BPS-rGO concentration or with the decrease in water/oil ratio. Using BPS-rGO to stabilize Pickering w/o emulsions is an effective and versatile approach to fabricate active materials that can be employed as catalysts for chemical reactions.