The invention discloses a train accident emergency monitoring system which comprises vehicle-mounted devices, a ground reading device, a base layer local area network, a computer network, a vehicle section local area network, an application and data server and a train detection field monitoring room local area network. Each vehicle of a train is provided with the corresponding vehicle-mounted device. The ground reading device is arranged along a train running line. When the train passes through the ground reading device installed on the line, the vehicle-mounted devices upload acquired pressure data of air braking systems of the corresponding vehicles to the ground reading device, and the ground reading device then transmits the data to the computer network through the base layer local area network. Data acquisition devices in the vehicle-mounted devices acquire the key point pressure change conditions in the braking and relieving processes of vehicle air braking in real time, reliable real-time data are provided for a user to find the accidently-braked vehicle, the bad-relieving vehicle and the train accidental emergency induced vehicle, and the safety of vehicle running is effectively improved.