CO discharged by mine flame-proof vehicles can result in wrong signals to the early-warning system of spontaneous combustion often occurred in coal mines as CO is one of the index gases when forecasting and early warning coal spontaneous combustion in underground mine. Traditional method is to install sensors in the air intake system to monitor the CO concentration. In the present paper, a number of CO distribution simulations are performed using commercial FLUENT software. When a mine flame-proof vehicle running at a speed of 7 m s(-1) in an underground tunnel while the inlet velocity of roadway is 3 m s(-1), dynamic distribution of CO concentration discharged by mine flame-proof vehicle within t = 1 -5 s is obtained, and variation of CO concentration on static monitoring points is obtained at the same time while simulating. The simulation results indicate that: the region of CO concentration greater than 0.0024% was in the scope from vehicle tailgate to the back which is irregular shapes, and it reduces to less than 0.0024% in short time, about 1 s. In front of the vehicle CO concentration is always a fixed value or even lower than 0.0019%. For comparative analysis, 4 monitoring points are arranged to monitor the CO concentration in actual underground roadway. And the actual measured data verified the correctness of numerical simulation data. (C) 2015 Elsevier Ltd. All rights reserved.