Among the graphene family, bilayer graphene (BLG) exhibits more diverse electronic structures and higher tunability than monolayer graphene due to its unique interlayer coupling effect, emerging as a crucial branch in functionalization research. By utilizing its interlayer as an embedding channel, BLG avoids impairing graphene's intrinsic conductivity-a common issue with surface modification. Furthermore, the interlayer coupling allows for synergistic engineering of its electronic structure, yielding performance superior to that of monolayer graphene. Therefore, the interface of BLG represents a potential functionalization site. Based on the aforementioned research status and issues, all calculations in this study are performed using density functional theory (DFT) via the Vienna Ab-initio Simulation Package (VASP). To accurately describe the van der Waals (vdW) interactions (π-π stacking) between the layers of AB-stacked BLG, the DFT-D3 method is employed for vdW correction to investigate the influence of functional groups on BLG electrical properties. This study focuses on four functional groups (-OH, -CO, -CHO, and -COOH), whose contained O and H atoms can readily form chemical bonds with the carbon atoms in BLG. Through interlayer modification, the interactions between these functional groups and the carbon atoms are analyzed to realize the regulation of interlayer coupling and electronic structure characteristics of BLG. The insertion of -OH and -CHO into the interlayer of BLG results in higher stability and lower interfacial binding energy, whereas the insertion of -CO and -COOH leads to reduced stability. The Fermi level of BLG shifts to varying degrees upon the insertion of functional groups. Specifically, the insertion of -OH or -COOH causes the Fermi level to shift toward lower energy levels, reducing the highest occupied energy level. In contrast, the insertion of -CO or -CHO shifts the Fermi level toward higher energy levels, exciting more electrons to higher energy states and resulting in electron filling at elevated energy levels. The band structure of BLG undergoes significant modifications due to the insertion of functional groups. The original parabolic band dispersion is disrupted, and the band distribution becomes more complex, with altered line trajectories and crossing characteristics. Partial density of states (PDOS) and charge density difference calculations reveal orbital hybridization and charge transfer between the functional groups and BLG. All four functional groups form covalent bonds with the carbon atoms of BLG, exhibiting characteristics of chemical adsorption. Moreover, the extent of charge transfer and the perturbation of charge density vary significantly among the different functional groups. This study aims to elucidate the regulatory mechanisms and underlying principles of functional groups, providing a theoretical basis for designing BLG-based electronic materials with specific functionalities, while also enriching the research framework of interlayer functionalization in two-dimensional layered materials.