The invention provides a press mounting apparatus and press mounting method of a semiconductor valve string. The press mounting apparatus comprises a horizontal workbench arranged on a frame, the horizontal workbench is provided with a guiding support mechanism used for guiding and supporting each device in a semiconductor valve string to be press-mounted, a force application mechanism is arranged at the end of a guiding direction on the frame, and the force application direction of the force application mechanism is the same as the guiding direction. The advantages are as follows: each device in the semiconductor valve string is horizontally placed on the guiding support mechanism for assembling, compared to a conventional vertical accumulation placement method, the method reduces transport paths, and therefore, the labor intensity is low and the assembling efficiency is high. Besides, the semiconductor valve string does not have to be hoisted and moved after being assembled, pressure loading can be carried out directly by use of the force application mechanism, the press-mounting efficiency and the automation degree of the whole press-mounting operation are improved, and the press-mounting precision is effectively guaranteed. At the same time, the height of the horizontally arranged semiconductor valve string is greatly reduced, and the press-mounting stability of the semiconductor valve string is improved.