In order to obtain the fire parameters of cable tunnels and study the time-dependent and spacedependent distribution of the air temperatures and fire smokes inside the tunnels, cable tunnel model is established and fullscale fire simulation is made by means of FDS (Fire Dynamics Simulator) developed by NIST (National Institute of Standards and Technology). The distribution pattern of the smoke density, oxygen density and temperature are obtained by means of processing and analysis of the experiment data, so as to provide some effective methods for fire-fighting, rescuing and escaping. Furthermore, some suggestion is made on fire prevention.