The invention provides an ultrahigh-speed (subsonic) rail transit system driven by air pressure difference. The ultrahigh-speed (subsonic) rail transit system comprises a tunnel, capsule compartmentsand tunnel valve mechanisms, wherein the tunnel comprises a plurality of unit sections which are sequentially connected, and each unit section is provided with the tunnel valve mechanism; the capsulecompartment is arranged in the tunnel formed by the unit sections in a sliding manner; airtight skirts at the front end and the rear end of the compartment are matched with the inner walls of the unitsections; when the tunnel valve mechanism works, a negative pressure environment is generated in front of the compartment, so that the air resistance is greatly reduced; when an air compressor in thecompartment works, an air cushion is generated between the compartment and the track to eliminate mechanical friction force; when the tunnel valve mechanism works, an air pressure difference is formed between the front end and the rear end of the compartment to drive the compartment to move at a high speed. The rail transit system is used for solving the problems that an existing air cushion train or magnetic suspension train are complex in structures, high in manufacturing costs and high in operation costs, a large amount of energy needs to be consumed, and the running speed is difficult tobe continuously increased.