Abstract: Aiming at the shortage of benzidine isotope internal standard reagents in environmental monitoring and food safety detection, an efficient synthetic method for stable isotope deuterium-labeled benzidine-D₈ was developed. Benzidine-D₈ was synthesized via two-step reactions: reduction of nitrobenzene-D₅ to hydrazobenzene-D₁₀ under alkaline conditions with zinc powder, followed by acid-catalyzed intramolecular rearrangement. The total yield of benzidine-D₈ was 50.3% based on the molar amount of starting material nitrobenzene-D₅. The product was characterized by HPLC and ESI-MS, with a chemical purity of 99.7% and deuterium isotopic abundance of 99.8 atom%. The results indicate that the synthesized benzidine-D₈ is suitable as an internal standard for the quantitative determination of benzidine residues in soil, water and textile samples.