The utility model discloses a transfer relay construction transfer device for a narrow site of a box girder tunnel portal. The device comprises at least two groups of switching cross beams and four groups of support switching devices, the supporting switching device comprises an upper cross beam, a left guide column, a right guide column, a fixing support and a bearing oil cylinder. Pin shaft holes which are uniformly distributed are formed in the left guide column and the right guide column in the vertical direction; the left bearing pin shaft, the pin shaft hole of the left guide column, theright bearing pin shaft and the pin shaft hole of the right guide column form a first limiting structure, and the second limiting structure is composed of a bearing part matched with the left bearingpin shaft or the right bearing pin shaft and a limiting part for limiting the freedom degree of the left bearing pin shaft or the right bearing pin shaft in the horizontal direction. The two groups of switching cross beams and the four groups of supporting switching devices are matched with each other, so that the safety and the stability of box girder transferring are greatly improved, and the working efficiency is improved.