The invention relates to a flame-retardant antibacterial master batch and a preparation method thereof. A metal modified hyperbranched polymer and other components are evenly mixed, then the mixture is molten and extruded to prepare the flame-retardant antibacterial master batch, the metal modified hyperbranched polymer is a network polymer formed by crosslinking a hyperbranched polymer containingcarboxyl at end groups and metal ions, has insoluble and non-fusible characteristics, is not solved in most organic solvents under 80 DEG C and is not fused in the range from room temperature to T, Tis greater than or equal to 370 DEG C, and crosslinking is achieved by connecting oxygen atoms on double bonds in the hyperbranched polymer containing carboxyl at end groups with the metal ions through coordinate bonds and connecting acid radical irons at the ends of molecules of the hyperbranched polymer containing carboxyl at end groups with the metal ions through ionic bonds. The metal modified hyperbranched polymer is evenly dispersed in the prepared master batch. The method is simple and easy to operate, the shortcoming is overcome that a traditional hyperbranched polymer cannot serve asa functional additive in the master batch, and the flame-retardant and antibacterial properties of the prepared master batch are good.