An installation auxiliary device of a radiator oil cooling tube connecting tube comprises a base. The base is fixed to a workbench. A supporting column is fixed to the base. A sector support is fixed to the upper end of the supporting column. A sector groove cavity penetrating through the arc side face of the sector support is formed inside the sector support. Sector annular grooves penetrating through the upper end face and the lower end face are formed in the portions, close to the arc side face, of the sector support. One end of an auxiliary rod penetrates through the sector groove cavity of the sector support and is hinged to the sector support through a hinge pin and a groove hole is formed in the other end face of the auxiliary rod in a turning mode. A bolt is arranged on the auxiliary rod, penetrates through the sector annular groove in the lower end plane of the sector support, the auxiliary rod and the sector annular groove in the upper end plane of the sector support in sequence and is connected to a nut in a threaded mode. A handle is welded to the nut. According to the installation auxiliary device of the radiator oil cooling tube connecting tube, the connecting tube can be installed just through one person, so that resources are saved, the device is fixed to the same position of different connecting tubes and suitable for installation of the connecting tubes at various angles, the process of repeated angle correction conducted by a worker is avoided, and the production efficiency is improved.