The invention discloses a long-span steel truss suspension bridge jointing method and device. A steel truss suspension bridge is constructed from two ends of the bridge and steel trusses are jointed at the middle part of the bridge. The method is characterized in that in the jointing process, vertical error of the joined steel trusses is adjusted on the steel trusses through a height lifting device, longitudinal error of the steel trusses is adjusted through a length traction device, and transverse error of the steel trusses is adjusted through an opposite-pulling device. With the adoption of the method and the device, in the jointing process of the steel truss suspension bridge at the middle, possible various errors can be adjusted so that bolt holes of jointing connectors can be aligned accurately and all poles of the steel trusses can be mounted. The method and the device have the advantages that the adjusting method is simple, jointing equipment is simple, the construction period is short, the construction accuracy is high, and the application range is wide.