The utility model relates to upright pillar assembly for a hydraulic support, particularly to a machine for vertically pressing and assembling an upright pillar, which is used for assembling a middle cylinder and a movable pillar of the upright pillar into an outer cylinder body, and solves the problems of high labor intensity, time and labor wastage and the like during upright pillar assembly of workers. The machine comprises a track and a portal frame capable of moving along the track, wherein a vertical placement bin for vertically placing the outer cylinder body of the upright pillar is arranged below the track; a fixation device for fixing the outer cylinder body of the upright pillar is arranged in the vertical placement bin; a movable beam is arranged on the portal frame; and hydraulic jacks used for controlling the movable beam to move up and down along with the portal frame are vertically arranged on the two sides of the portal frame. The machine has the advantages of simple and reasonable structure, convenient operation, safety, reliability and strong practicability, can effectively reduce the labor intensity in the assembly of the upright pillar of the hydraulic support, improves the assembly quality and efficiency of the upright pillar of the hydraulic support, and has great practical meaning in production.