The invention provides a stable kit for detecting homocysteine. The stable kit consists of a reagent R1 and a reagent R2, wherein the reagent R1 comprises the following components: a buffering solution, a mercaptan reducing agent, lactic dehydrogenase, serine, reducing coenzyme, a surface active agent, a stabilizing agent and a preservative; and the reagent R2 comprises the following components: a buffering solution, cystathionine beta-synthase, cystathionine beta-synthase, a surface active agent, a stabilizing agent and a preservative. The stable kit provided by the invention can detect the homocysteine in serum by utilizing an enzymatic cycling method, is easy to operate, and is fast, accurate, sensitive and stable.