The invention relates to a method for chlorinating and extracting gold in arsenic-containing sulphuric acid slag and comprehensively utilizing gas heat. The method comprises the following specific steps of (1) acid leaching and arsenic sulfide precipitation; (2) drying, wet-grinding, pelletizing, drying and chloridizing volatilization; (3) primary quench cooling, heat exchanging, secondary quenching and electrostatic precipitation; and (4) dust scrubbing, chloride leaching of gold, gold reducing, silver extraction by ammonia leaching and silver reducing. An acid leaching and arsenic precipitation technology is adopted, and arsenic is first separated from raw materials, so that the influence of arsenic on a follow-up system is eliminated. The arsenic sulfide precipitation technology realizes enrichment of arsenic in water and recycling of water. The primary quench cooling technology is adopted, so that the temperature of dust-laden gas is higher than that of a softening point of dust, and relatively high liquidity is obtained. An iron powder replacement technology is adopted, so that gold and silver enriched in recycling process water are recycled. Lead and zinc in the process water are recycled through alkaline lead and zinc precipitation, so that the problem that a pipeline is blocked with soluble salt is solved.