Abstract: The ¹⁵N labeled hydrazine hydrate is a strong reducing agent in the synthesis procedure of stable isotope labeled compounds, and it has been widely used in the isotope-labeled pharmaceutical synthesis. The reaction conditions of ¹⁵N labeled hydrazine hydrate were mainly investigated by single-factor design, and the following optimized conditions were obtained: the concentration of available chlorine was 115-120 g/L, the chlorination reaction time was 30~40 min, the reflux time was 7 min, and the mass ratio of material was m(catalyst) ∶m(urea) =1.0∶10.0, and the yield of ¹⁵N labeled hydrazine hydrate was 76.1%, the abundance of ¹⁵N was 99.20%.