The invention discloses an automatic medicine distributing box mechanism which comprises a medicine box body. A door opening device is arranged at one end of the medicine box body, and a medicine outlet is formed in the other end of the medicine box body. A counting device is arranged on the lateral portion of the portion, at the medicine outlet, of the medicine box body. A plug pin hole matched with a plug pin is formed in the other lateral portion of the medicine box body. The medicine box body comprises a mold opening profile with a U-shaped section. The concave part of the U-shaped mold opening profile serves as a medicine storage area used for storing medicine. Second installation grooves are formed in the two inner sides of the bottom of the mold opening profile. Installation holes are formed in the two side walls of the mold opening profile. First installation grooves are formed in the two inner sides of the upper portion of the mold opening profile. A thickness control block, a length control block and a sliding block are arranged in the medicine box body. The sliding block is driven by a micro motor arranged at the medicine outlet. By the adoption of the automatic medicine distributing box mechanism, the requirement for high-efficiency automatic medicine fetching and distributing can be effectively met, medicine distribution is accurate, the working efficiency of medical workers is improved, and the working difficulty of the medical workers is lowered.