The application of medical magnesium (Mg) alloys in implantable medical devices is promising due to the similar modulus of elasticity and biodegradability to human bone, which facilitates osseointegration. However, rapid degradation and loss of mechanical strength remain critical issues. To tackle these challenges, in this study, liquid metal gallium (Ga), which possesses non-toxicity, excellent biocompatibility, moderate chemical reactivity, and superior alloying capability, was used to develop a novel Mg alloy coating that can simultaneously enhance mechanical strength, reduce the degradation rate, and provide antibacterial and osteogenic properties. A unique, simplified coating process applied liquid Ga to the surface of ZK60 Mg alloy, and coatings of varying thicknesses were successfully fabricated. The phase composition of the Mg-Ga alloy layers was identified mainly consisting of Ga₅Mg₂ and Ga₂Mg. Vitro corrosion tests demonstrated that surface alloying of Ga with ZK60 effectively suppressed the degradation rate of the Mg alloy. Prolonged Mg-Ga alloying time improved human bone marrow mesenchymal stem cells (hBMSCs) adhesion, spreading, proliferation, and differentiation. The Mg-Ga alloy layer positively affected the early differentiation of osteoblasts and extracellular matrix mineralization, upregulating the expression of osteogenic-related genes and inhibiting osteoclast activity. Additionally, the Mg-Ga alloy exhibited excellent antibacterial properties through a combined effect of ion release and the formation of an alkaline environment. In short, the Ga-coated ZK60 Mg alloy demonstrated superior corrosion resistance, structural stability, cellular compatibility, osteogenic performance, and antibacterial capability, providing strong support for applying Mg alloys in medical implants.