The invention relates to an auxiliary device for transformer mounting and a transformer mounting vehicle using the device. The auxiliary device for transformer mounting comprises a mounting rack, wherein a transformer mounting table for driving a transformer to move forwards and backwards is guided and assembled on the mounting rack in the front-and-back direction, a transformer fixing seat for fixing the transformer is arranged on the transformer mounting table, a fine tuning mechanism for enabling the transformer fixing seat to translate to realize centering of the transformer and a switch cabinet is arranged between the transformer fixing seat and the transformer mounting table. The problem that existing auxiliary devices for transformer mounting cannot adjust positions of transformer bolt mounting holes accurately is solved.