In the process of metal oxide desulfurization,partial hydrogen sulfide（H,2,S） is commonly converted into carbonyl sulfide（COS）,and COS has similar harm to H,2,S and is more difficulty to remove.ZnO/MCM-41 coal gas desulfurizer（hereinafter referred to as“desulfurizer”） with good desulfurization performance was prepared by sol-gel method.The formation behavior of COS in desulfurization process was studied on a fixed bed device,and the method of inhibiting COS formation by modification of Co additive was proposed.Then the phase composition and structure of desulfurizer were analyzed by XRD,XPS and other characterization methods.By comparing COS formation behaviors in different desulfurization atmospheres,it is found that COS mainly derives from the reaction of CO/CO,2, with H,2,S,and ZnS catalyzes the reaction of CO,2, with H,2,S.Meanwhile,there is no synergistic effect between the reaction of CO-H,2,S and CO,2,-H,2,S.The presence of H,2, inhibits the formation of COS.When the Co additive with the mass fraction of Co of 1%,3%and 5%are added to the desulfurizer,the COS production in the desulfurization process can be reduced by 69.0%,94.9%and 98.4%,which is mainly related to the catalytic effect of additive Co on COS hydrogenation.In addition,the sulfur capacity of desulfurizer is increased by 0.32%by adding the Co additive with 3%Co mass fraction.