A tunnel fire may gradually change from a fuel-controlled fire to a ventilation-controlled fire during the sealing process, so it is of great significance to study the influence of sealing time on the combustion state for safety control. In this study, an unsealed wood-crib fire test was first carried out using a reduced-scale tunnel model. When the wind velocity is 0.10 m/s, the wood crib is fuel-controlled. Based on this, the combustion state of a wood-crib fire was studied experimentally when the sealing time was 1 min, 3 min, 7 min, and 10 min. The results showed that after sealing, the flame orientation is approximately vertical, and as the sealing time increases, the carbonization of the wood crib becomes more pronounced. The ratio of X_CO/X_CO2 exceeds 0.057 1 min after sealing, and the wood-crib fire becomes ventilation-controlled. When the sealing time is 7 min and 10 min, the increase rate of X_CO/X_CO2 is faster than when the sealing time is 1 min and 3 min. The earlier the initial sealing time, the better the fire can be suppressed. During the sealing process, the temperature on the downwind side of the fire source decreases exponentially. This study aims to provide a reference for the application of sealing technology in tunnel fires.