Abstract: In terms of the S-CO produced by coal structure mechanical disruption,using coal mechanical breakage S-CO experiment combined with infrared spectrum experiment,this study investigated its formation rule and analyzed its formation mechanism. Results shows that when the coal sample qualities are same,the value of average CO production rate and CO concentration increase with the increase of motor rotational speed in N2 atmosphere. The changes of S-CO concentration can be divided into three periods under the experimental conditions:no S-CO production period,CO lin- early increase period and CO exponentially increase period. The authors analyzed the changes of chemical bonds of coal structure during the mechanical disruption process,based on the theory of coal chemistry and infrared spectrum a- nalysis. The multi-step reaction mechanism of S-CO was clarified according to the oxygen-containing groups and the dissociation energy corresponded. The unilateral recognition of predecessors’ research was corrected that “ S -CO is produced by the mechanical activation decomposition of carbonyl groups in coal”,and the formation mechanism of S-CO was supplemented as well.