The invention discloses a butt-jointing method for a truss girder, which comprises the following steps of: a, guiding a to-be-erected girder to move along the direction of an erected girder till move to a preset position by a guiding girder; b, removing the guiding girder section by section and moving the to-be-erected girder along the direction of the erected girder; c, stopping moving when a distance between ports of the two girders reaches a preset distance, measuring a deviation between the position of the to-be-erected girder and a design position, roughly adjusting the position of the to-be-erected girder, and calculating and confirming the distance between the two girders; d, moving the to-be-erected girder according to the calculated and confirmed distance, and finely adjusting the positions of an upper chord pipe and a lower chord pipe of the to-be-erected girder, thereby aligning the two girders; and e, welding a plurality of fixing plates on a contact surface of the two girders, wherein the two ends of the fixing plates are respectively in fixed connection with the two girders. According to the butt-jointing method for the truss girder provided by the invention, the girders can be butt-jointed in air, the manufacturing of the girder and the butt-jointing operation application are more convenient and flexible, and the safety coefficient of the butt-jointing operation is also increased.