<p>Sealing the tunnel entrance is one of the effective ways to control the fire in tunnels. The fire characteristics of tunnels with entrances sealed are greatly different under various sealing distance, sealing time, sealing ratio and heat release rate (HRR). The previous researches only focus on the influence of sealing ratio and sealing time on flame characteristics in the tunnel and did not consider sealing method, sealing distance and heat release rate, all of which directly impact the oxygen concentration in the tunnel, significantly affecting the flame combustion. In this work, we built a reduced-scale tunnel model to investigate the fire behaviors in the sealed tunnel; the major factors include sealing ratio, sealing method, sealing distance and heat release rate. The experimental results show that the flame tends to self-extinguish due to the less oxygen concentration with the tunnel entrances sealed. The greater HRR, the larger sealing ratio, the shorter sealing distance, the easier the fire in tunnels extinguish. Fire flame is easier to self-extinguish in up sealed tunnel comparing with the down sealed tunnel. It is found that there is a critical sealing ratio, at which the smoke temperature under the ceiling would reach the maximum; other than that ratio, the maximum smoke temperature would decrease. A theoretical analysis was performed to investigate the flame self-extinguishing time in fully sealed tunnels, and the correlation was established among the self-extinguishing time, heat release rate and sealing distance, which can approximately predict the self-extinguishing time of tunnel fires.</p>