The invention discloses a primary seed fermentation tank. The primary seed fermentation tank comprises a support and is characterized in that a jacket cylinder is fixedly mounted at the upper end of the support, an inner container cylinder is fixedly mounted in the inner cavity of the jacket cylinder, a stirring system is fixedly mounted on the upper end face of the inner container cylinder and at the center of the inner cavity of the inner container cylinder, a first compressed air connecting pipe and a discharge connecting pipe are arranged at the lateral upper end of the inner container cylinder, and a steam connecting pipe, a breathing pipe connecting pipe and a washing pipe connecting pipe are arranged on the jacket cylinder; a second compressed air connecting pipe and a material connecting pipe are mounted on the other side of the upper end face of the inner container cylinder, and a pressure detecting connecting pipe is arranged below the second compressed air connecting pipe. The primary seed fermentation tank has the advantages that that fact that seed fermentation is performed under a stable environment is sufficiently guaranteed by the steam connecting pipe, the breathing pipe connecting pipe, the washing pipe connecting pipe, the material connecting pipe, the pressure detecting connecting pipe, a sampling valve connecting pipe and a thermometer blind pipe, seed fermentation quality is increased, the fermentation tank is easy to clean, the fermentation of the next batch of seeds is facilitated, and production efficiency is increased.