A synthesis method for an L-heterocyclic amino acid and a pharmaceutical composition having the said amino acid are provided in the present disclosure. The synthesis method comprises: step A: preparing a heterocyclic keto acid, wherein the heterocycle in the heterocyclic keto acid is selected from any one of a five-membered heterocycle, a six-membered heterocycle, a seven-membered heterocycle, an alkyl-substituted five-membered heterocycle, an alkyl-substituted six-membered heterocycle, and an alkyl-substituted seven-membered heterocycle, and the keto acid group in the heterocyclic keto acid has a structural formula ofand is located on any one of the carbon positions of the heterocycle, and step B: mixing the heterocyclic keto acid with ammonium formate, a phenylalanine dehydrogenase, a formate dehydrogenase and a coenzyme NAD+, and carrying out a reductive amination reaction to generate L-heterocyclic amino acid, wherein the amino acid sequence of the phenylalanine dehydrogenase is SEQ ID No. 1.
