The invention provides a degradable antibacterial magnesium alloy and a preparation method of the degradable antibacterial magnesium alloy, and relates to the field of metal biomedical materials. Thedegradable antibacterial magnesium alloy comprises main active elements of Ag, Cu, Zn and Sr, and by means of composition optimization design of the magnesium alloy, the components comprise, by mass,1.35-1.65% of Ag, 0.9-1.1% of Cu, 3.6-4.4% of Zn, 0.9-1.1% of Sr, 0.36-0.44% of Ca and the balance Mg and other inevitable impurities. After the magnesium alloy material implant finishes the action, the magnesium alloy material implant can be completely degraded to avoid secondary operation removal, the medical cost and the pain of patients are reduced, the antibacterial property of the implant isimproved, and the magnesium alloy material implant has the functions of promoting osteoblast formation and inhibiting osteoclast bone absorption; the degradable antibacterial magnesium alloy adopts asemi-solid rheological die casting process, the microstructure of the product is uniformly distributed, the internal structure is compact, the defects of pores, segregation and the like are few, andthe requirements for high quality and high precision of implant products can be met.