The invention discloses a support device for erecting steel beam segments at high places and a construction system, and relates to the technical field of bridge steel beam construction. The device comprises a guide rail and a frame body arranged on the guide rail, The frame body comprises a bracket with a preset height, the bracket comprises at least three support columns, a cushion seat with a preset height is arranged on the support columns, and adjusting devices are arranged at the bottom of the support columns, and the adjusting devices are used for adjusting the height and the position ofthe support columns corresponding to the adjusting devices. The device for erecting steel beam segments at high places and the construction system of the steel beam segments transfer a large amount of original operations at high altitudes to the ground, thereby ensuring more safety and reliability in the construction process.