In order to study the safety evacuation mode of people in a large diameter shield tunnel under deep water, Nanjing Heyan Road Crossing Channel (South Section) is taken as an example. The tunnel adopts the method of alternate arrangement of stairs and slides to evacuate the crowd for the first time. To obtain the reasonable key parameters of evacuation facilities in the tunnel, the evacuation parameters and evacuation time are analyzed, and the evacuation condition of shield section is simulated. The results show that when evacuation slides and stairs are set alternately at 60m, the minimum evacuation time is 535s, which is less than the safe evacuation time 1800s. This paper can provide a reference of the evacuation mode for other tunnels.