If a train traveling in the tunnel is on fire,the corresponding emergency plan is usually to make the train continue running to the next station as far as possible，instead of stopping in the tunnel.This paper takes a moving on-fire train in subway tunnels as the research object,and uses the channel Couette flow,the heat and mass transfer and the combustion reaction kinetics to explore the combustion characteristics of the fire affected by such two factors as the air quantity in the annular space between the tunnel and the train and the piston wind in the tunnel,followed with some small-scale model experiments.Then,the return air quantity is derived,and the relationship between the fire heat release rate and the running speed of the train is modeled.Finally,a reasonable speed for the on-fire train,which keeps the fire heat release rate at a relatively low level，namely 48km/h,is suggested.The research achievements and the proposed method provide theoretical guidance for the emergency rescue of the on-fire train in subway tunnels.