In order to study the effects of the marine bioactive peptide on the formation of marine bacterial biofilm and settlement of the marine mussel juveniles, this study investigated Mytilus coruscus juvenile response stimulated by agarose encapsulation with different concentrations of M. galloprovincialis peptide and observed its induction capacity on M. coruscus juvenile settlement. Then, two strains of marine bacteria with different settlement induction abilities were selected including Pseudoalteromonas marina and Leisingera aquaemixtae. Different concentrations of M. galloprovincialis peptide were added into the bacterial fluid during biofilm formation. The effects of M. galloprovincialis peptide on biofilm formation and biological characteristics were analyzed. Meanwhile, the effect of biofilm changes on M. coruscus juvenile settlement was studied. The result of M. coruscus juvenile settlement bioassays showed that M. galloprovincialis peptide could significantly induce M. coruscus juvenile settlement (P<0.05). Besides, the effect of 1.0 g/L M. galloprovincialis peptide which was added during the formation of biofilm on settlement induction of M. coruscus juveniles was the most significant (P<0.05) and the effect of 10.0 g/L M. galloprovincialis peptide on settlement of M. coruscus juveniles was lowest (P<0.05). In further experiment on biofilms, such as biofilm bacterial density counting, biofilm thickness measurement and confocal laser scanning of extracellular products of biofilms, it was found that the induction effect of 1.0 g/L M. galloprovincialis peptide was most significant (P<0.05) and 1.0 g/L M. galloprovincialis peptide significantly increased the bacterial density and exoprotein content of biofilms (P<0.05). However, 10.0 g/L M. galloprovincialis peptide was significantly decreased the bacterial density and protein content of biofilms (P<0.05). The results showed that M. galloprovincialis peptide could directly affect the settlement of M. coruscus juveniles and indirectly affect the settlement of M. coruscus juveniles by affecting the biofilm formation level and exoprotein content of marine bacterial biofilms. These results provided a new insight for exploring the role of marine bioactive peptides in settlement of M. coruscus juveniles. This study provided a new approach for studying the physiological function of bioactive peptides from marine shellfish.