Abstract: Since air in natural gas purification plant of Puguang gas field contains a certain amount of H₂S and SO₂, corrosion of air conditioning equipment is serious. Besides, there are some defects in existing HVAC system. In order to improve the running effect of HVAC system and meet the needs of personnel and equipment to temperature and humidity, the technology optimization of the HVAC system was conducted. In details, separate air duct system was installed in the equipment room and staff room of the central control chamber respectively to realize the cooling by "man-machine separation"; six constant temperature and humidity units and more than three sets of air conditioning unit were replaced, as well as the adoption of efficient chemical air purification unit and the addition of three sets of fire smoke exhaust system, so as to satisfy the demand of the internal staff and equipment for safe operation.