Abstract: According to CO content over limit occurred in No. S205 fully- mechanized top coal caving mining during the period of the terminal mining and the power ed supports withdrawing in Qinyuan Mine and the spontaneous combustion of coal left in the goaf, from the geological structure of the coal mining face, coal quantity lef t, ventilation leakage and other aspects, the paper analyzed the abnormal causes of CO in the air returning flow. According to the actual conditions of the coal mining fa ce and the features of each fire prevention and control technology, based on the principles to quickly reduce ventilation leakages in the goaf, in order to reduce the oxy gen content in the goaf and to eliminate high temperature points, a comprehensive fire prevention and control technology mainly with the local ventilation, high level bor ehole grouting and high polymer gum injection in the boreholes in front of the powered supports was conducted to reduce the CO volume fraction in the air returning flo W below 24 x 10- 6and to ensure the safe withdrawing of the powered supports from the coal mining face.