Abstract: Aiming at CO overrun problem of return corner in mining face of Shendong Mining Area, on the basis of research and field observations, it obtained that CO sources of return corner mainly included float coal oxidation in the goaf, crushing coal as shearer cutting coal, rubber-tyred vehicle exhaust generated, float coal low-temperature oxidation in the goaf was the main source among them. It provided a basis for taking appropriate overrun control technology measures.