Removal of COS is more difficult than that of H2S from coal gas. It has been found that the reactions of H2S to COS may take place in sulfidation tests of sorbent at high temperatures. The formation of COS at high temperatures in simulated coal gas without sorbent and removal of COS with sorbent was mainly discussed in this article. A series of experiments were carried out by changing the composition of feeding gas and the temperature of the reactor. The results showed that the reactions of H2S to COS occurred when the feeding gas was blended with CO and H2S, or CO2 and H2S. Gas H2S, CO, and CO2 have obvious contributions to the formation of COS and the reaction of H2S and CO is dominating, while H2 and H2O are negative effects in the temperature range of 623-873 K. It was also proven that the concentration of COS in outlet gas decreased dramatically when the iron-based sorbent was packed in the reactor. Iron-based sorbent is active to remove COS from hot coal gas, though the ability of deep removal of COS decreased with increasing temperatures from 723-873 K.