The invention belongs to the technical fields of plastic modification and processing and particularly relates to an efficient halogen-free enhanced flame-retardant functional master batch which can bedirectly applied to the direct injection molding of PC-ABS alloy products and a preparation method of the master batch. The multifunctional master batch is formed by the combination of a master batchA and a master batch B, wherein the master batch A contains the following components in percentage by weight: 50.0wt%-60.0wt% of glass fibers, 20.0wt%-25.0wt% of high-flow PBT resin, 10.0wt%-15.0wt%of ABS resin, 5.0wt%-10.0wt% of a thermoplastic styrene elastomer, 2.0wt%-3.0wt% of styrene-maleic anhydride random copolymer, 1.0wt%-2.0wt% of hyperbranched polyester and 0.1wt%-0.3wt% of an antioxidant. Compared with a traditional plastic functional master batch, the prepared functional master batch has the advantages that the mutual loss of the modification effects caused due to the mutual shear loss between the glass fibers and the flame retardant in the processing process is avoided, and compared with a traditional enhanced halogen-free flame-retardant system, the modification effects ofthe two systems are remarkably improved; and the multifunctional master batch has the characteristics of easiness in dispersion and processing and can be subjected to injection molding after being simply mixed with PC-ABS alloy resin.