Achieving stable, efficient p-type conductivity in β-Ga₂O₃ remains a long-standing challenge, rooted in its intrinsically flat valence band and the deep acceptor levels introduced by conventional dopants.Herein, we systematically investigate the modulation mechanism of p-type conductivity in two-dimensional (2D) β-Ga₂O₃ via the introduction of V_Ga-nH (n=1–4) complex defects, using first-principles calculations based on density functional theory (DFT) within the projector augmented wave (PAW) framework and generalized gradient approximation (GGA-PBE). Calculated defect formation energies reveal that multi-hydrogen complexes, particularly V_Ga-3H and V_Ga-4H, exhibit negative formation energies under both Ga-rich and O-rich growth conditions,confirming their thermodynamic favorability.Unlike isolated gallium vacancies (V_Ga), which fail to introduce effective shallow acceptor levels in the 2D system, V_Ga-nH complexes induce shallow acceptor transition levels; specifically, V_Ga-3H and V_Ga-4H exhibit transition levels located 0.16–0.26 eV above the valence band maximum (VBM), indicating significant potential for enhancing p-type conductivity. Further electronic structure analysis, based on projected density of states (PDOS), demonstrates that hydrogen incorporation induces pronounced orbital hybridization between H and adjacent O atoms, forming O-H bonds and generating defect states proximal to the VBM. This indicates that hydrogen actively participates in defect-state reconstruction rather than serving a simple passivation role. To further optimize p-type characteristics, we explore co-doping with metal elements (Ag, Mg, Zn), finding Ag co-doping to be the most effective strategy, as it drastically lowers acceptor transition levels. Notably, the V_Ga-3H-Ag complex introduces an ultra-shallow acceptor level at merely 0.006 eV (6 meV) above the VBM, enabling ready thermal activation of acceptors at room temperature. These findings unveil a synergistic defect engineering strategy based on V_Ga-H complexes and metal co-doping, offering a promising pathway to overcome the intrinsic limitations of p-type doping in β-Ga₂O₃. This work provides critical theoretical insights for the design of high-performance p-type ultra-wide-bandgap oxide semiconductors.