The invention discloses a supported silver-carbon catalyst for salt electrolysis, which is characterized by being solid powder. Silver particles with the particle size being 3-10nm are loaded on the surface of acidified carbon black particles through uniform dispersion, the silver loading factor ranges from 40 percent to 400 percent, and the mass ratio of the silver and the acidified carbon black particles is 0.4:1-4:1. The preparation method adopts chemical reduction and comprises: pouring silver ammonia solution and hydroxide sodium solution in sequence into a reaction system which consists of glycol and acidified carbon black, mixing well, condensing and refluxing at the certain reaction temperature to obtain the reaction product, black solution, and finally obtaining black solid powder through centrifugation or filtration washing and drying.