Box shaped parts are always difficult in forming. For a rectangular fireproof hood, the problems of strip positioning and distance control，die forming and shaping, automatic discharge etc. appeared in box shaped parts forming by multistage forming die were studied. According to the structure requirements of fireproof hood, the layout of multistage forming die for fireproof hood was optimized, and multistage forming die was designed. The die assembly was simulated by software UG，which ensured the accuracy of the die assembly. The difficulty of automatic unloading for multistage forming die was solved by the punch structure with dovetail groove combination forming. The production of proof proves that the multistage progressive die for fireproof hood is of high production efficiency and smooth feeding. So the flat formed parts are obtained and fully meet the requirements of customers.