Abstract: In order to study the change law of smoke characteristics in the dynamic sealing process of coal mine roadway fire, FDS software was used to conduct full-scale numerical simulation of mine roadway fire, and the CO volume fraction decay rate model of roadway fire was established by scale experiment. The transverse and longitudinal temperature distribution and smoke spread law in the sealing process of 50% to 100% of the roadway were established, and the CO volume fraction attenuation model was established to predict the fire extinguishing time after the roadway was completely sealed. The results show that during the change of sealing ratio from 50% to 100%, the temperature at the center of the ceiling first sharply decreases and then slowly increases; after being sealed, the temperature above the fire source shows a distribution pattern of high temperature above and low temperature below, and the closer it is to the fire source, the faster the temperature decay rate; the vertical distribution of ceiling temperature shows an overall increase, the maximum temperature point shifts 1-3 m to the sealed side; the deposition phenomenon of smoke on the sealed side is obvious, and the stratification phenomenon disappears; the relationship between CO volume fraction and time is linear when one side is completely sealed. According to the CO volume fraction decay rate model, it is predicted that the ignition source of 2, 3 and 4 MW is extinguished after 103.16, 94.40 and 86.21 s, respectively.