The invention discloses a preparation method of D-cationic chiral amino acid methacrylate copolymer. The D-cationic chiral amino acid methacrylate copolymer is prepared through block copolymerizationof monomer D-lysine methacrylate and D-leucine methacrylate. The method comprises the following steps of: carrying out homopolymerization on a first D-type amino acid monomer, using dithiobenzoic acid-4-cyan valeric acid as a chain transfer agent and azodiisobutyronitrile as an initiator for RAFT polymerization, using a D-configuration amino acid monomer polymer macromolecular chain transfer agentand azobisisobutyronitrile as the initiator, and adding the initiator into a second D-type amino acid monomer to carry out RAFT polymerization to obtain the block copolymer of the D-lysine methacrylate and D-leucine methacrylate. The polymer has excellent antibacterial performance and can obviously destroy the structure of a bacterial membrane to cause the death of bacteria; hemolysis experimentsand in vitro smooth muscle cell compatibility experiments show that the copolymer keep obvious biocompatibility.