Analyzed are such shortages existing in previous engineering design of molecular sieve dehydration unit as unreasonable technological process, high energy consumption and equipment damage, identified are causes resulting in such shortages and proposed are specific solutions. Optimized is technological process of regeneration gas, changed are materials of regeneration gas pipelines and cooler as well as regeneration gas compressor so as to avoid corrosion of H2S on these equipments, changed is the bottom support structure of molecular sieve dehydration tower so as to ensure normal operation of process unit, and changed is the structure of regeneration gas heating furnace so as to improve thermal efficiency of the heating furnace, which reduces energy consumption of the furnace greatly and achieved is the purpose of energy conservation and environmental protection.