The invention discloses a tramcar intersection red light running alarm system and alarm realization method. According to the system, ground information is transmitted to vehicle-mounted equipment through vehicle-ground wireless communication when a tramcar is away from an intersection for a section of distance so that pre-alarm of the traffic signal of the intersection is realized, and a speed threshold is set for guiding a driver to control operation speed of the tramcar; if operation speed exceeds the speed limit, the driver is prompted to implement common braking, and braking is released after reduction of speed so that the tramcar is ensured to stop before the red light; and whether the tramcar can pass the intersection under allow light with maximum sufficient time is judged by utilizing remaining time of the signal light so as to ensure using of the speed threshold for guiding the driver to drive. A situation that the tramcar enters the intersection and conflicts with municipal vehicles at the intersection due to the fact that the driver customarily controls the tramcar and is liable to exceed speed at the aggressive red light signal of the intersection in a big and long interval can be effectively prevented so that safe driving can be guaranteed and operation efficiency and route passing capacity of the tramcar can also be enhanced.