The invention discloses an access control system and method based on fire alarm. The access control system comprises a communication server, a fire sensor, a fire extinguishing module and a fire-fighting channel access control module, wherein the communication server comprises a data storage unit, a central processing unit, a temporary storage unit, a clock module and an alarm unit; the fire sensor comprises an ultraviolet sensor and a smoke sensor; the smoke sensor is a photoelectric induction sensor; the smoke sensor is used for acquiring smoke concentration and sending smoke acquisition information to the central processing unit; the fire extinguishing module comprises a water spray unit and a flow speed regulating unit; and the fire-fighting channel access control module is a fire-fighting channel safety door. According to the access control system disclosed by the invention, the fire-fighting channel safety door is associated in the fire alarm system, the safety door is intelligently opened when the fire happens, and people is reminded to evacuate through alarm, so that staff quantity for managing the safety door is reduced, and therefore, the access control system is convenient and intelligent, effectively improves fire alarm processing cavity, and provides convenience for the fire-fighting monitoring field and the fire-fighting control field.