The invention discloses a method for defining the dangerous working condition of an automobile and performing collision avoidance control. A system based on the method comprises a detection radar, a camera, a vehicle speed sensor, a yaw velocity sensor, a front wheel corner sensor, a dangerous working condition judgment module, a road adhesion coefficient estimation module, a collision avoidance control module, a steering execution mechanism, a braking execution mechanism and an execution control unit. During work, the road adhesion coefficient estimation module estimates road adhesion coefficient firstly, the road adhesion coefficient, vehicle speed and the relative distance of two vehicles are input into the dangerous working condition judgment module, the emergency working condition isjudged to be which one of four working conditions of collision avoidance through braking, collision avoidance through steering, collision avoidance through coordination and unability to collision avoidance, and active avoidance is realized by adopting different collision avoidance methods. By the method, self-adaptive active collision avoidance is guaranteed under the emergency working condition or under the bad conditions of road mutation and the like, and the problem about emergent collision avoidance under the extreme severe environment can be solved effectively.