The invention discloses a subway digital audio-video broadcasting method and system based on compressed sensing. The method adopts the ARM Cortex-M digital broadcasting technology based on the compressed sensing real-time security algorithm of a RS485 bus, and has the functions of realizing intercom in a cab, broadcasting to passengers by a driver, realizing conversation between the driver and the passengers, communicating with an over-ground control center by the driver, digitally broadcasting stops/alarming for close the door and like. The whole system adopts the full-digital processing technology and adopts the real-time security algorithm based on the compressed sensing technology; the original audio-video data is compressed by use of the compressed sensing technology, the data size is reduced, and a frame information table is established for media data frames; by use of the dynamic and static combined RS485 bus scheduling algorithm, the data and instructions with high real-time can be sufficiently considered so as to be preferentially transmitted, and the channel can be sufficiently utilized; and the real-time property of the system communication is greatly improved.