In this work, we report that the Ag-graphene composite (AGC) can effectively enhance the light harvesting and photoluminescence (PL) quenching efficiency of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV). Loading the AGC on MEH-PPV leads to improved light absorption ability and PL quenching efficiency, which is due to the strong interaction between localized surface plasmon resonance (LSPR)-activated Ag nanoparticles and the MEH-PPV molecule. Control experiment reveals that the combination of graphene and Ag nanoparticles achieves superior light absorptivity and PL quenching ability compared with individual graphene and Ag NPs. The exponential shape of the Stern-Volmer plot implies that both Ag and graphene in the AGC can offer the quenching pathway for the PL quenching process. We also found that the AGC with a broader LSPR absorption range is competitive in enhancing the light absorption ability and PL quenching efficiency of the MEH-PPV-AGC composite, because it can expand LSPR-induced light harvesting and PL quenching response to a wider absorption range.