The utility model provides a cargo transportation semi-trailer train with suspension arm support device, which comprises a mainframe and a connection framework. The mainframe is removable and is connected with the connection framework, while the suspension arm support device is connected with the connection framework. The suspension arm support device comprises a pair of support bars. The support bars are all in form of reversed ''L'', and the reversed ''L'' sides of the support bar is freely connected with the both sides of the connection framework and in symmetry with the longitudinal central side of the connection framework. The support bars have the relation with the connection framework cross direction sides that relating to this position, the moment of the connection framework for this main framework is smaller than or equal to the moment of the mainframe reversing to the connection framework, which can effectively prevent from overturn accident.