The invention provides a control method, device, a controller and an automobile of an automatic emergent braking system and relates to the technical field of automobiles. The method is applied to a module of range radar MRR in an automatic emergency braking system. The method comprises following steps: obtaining distance data from adjacent vehicles in the direction of travel when it is detected that a car is on adaptive cruise; when the distance data is less than a first preset distance, executing an early warning flow; when the distance data is less than a second preset distance, executing anautomatic emergent brake flow; the second preset distance is less than the first preset distance. According to the invention, the automatic emergent braking is realized under the adaptive cruise state.