To solve design problems of the block-hole graphite heat exchanger, this paper demonstrates the features of a 40 m2 hydrochloric acid preheater used in project, such as material properties, internal components, operating principles and structure points. The heat exchanger block, the head block, the steel container, and the holding-down device are introduced in detail. The adaptable material is recommended. This paper also gives out the structures of hole, seal and clamp. And the stress analysis model of holding-down device is proposed. It is found that the maximum bearing capacity and the minimum sealing capacity must meet allowable requires during calculating the spring preload. This solution provides a practical case for the design optimization of such equipment. It is theoretical guiding significance to the further research of block-hole graphite heat exchanger.