The invention relates to the technical field of bottom-door train detraining and discloses a detraining system and method for a bottom-door train. The system comprises a plurality of door opening stops, multiple groups of door opening proximity switches and a control device, wherein the door opening stops are separately arranged at initial ends of a plurality of funnels of an unloading station; the multiple groups of door opening proximity switches are separately arranged at the initial ends of the funnels along a rail track in a one-to-one correspondence manner, each group of door opening proximity switches comprises two door opening proximity switches, the distance between the two door opening proximity switches of each group is equal to that between two groups of wheels of a bogie of each carriage, and proximity signals are sent when the wheels of the bogies are induced; the control device is used for controlling the rising and falling of the door opening stops according to the proximity signals simultaneously sent from the corresponding two door opening proximity switches of each of the multiple groups of door opening proximity switches, so as to control a plurality of carriages to be subjected to unloading. By the technical scheme provided by the invention, the opening and closing of bottom doors of the carriages can be automatically controlled, so as to achieve automatic uniform unloading while carrying out traveling.