The invention provides an auxiliary support device of an optical measurement system. The auxiliary device comprises a three-leg support, support hinges and a dovetail groove fixation platform; the three-leg support is connected with and supports the optical measurement system and adjusts measuring direction and angle of the system; the support hinges compensate the opening angle of the three-leg support so that the connecting directions in connecting points are vertical to the connecting surface always to realize stable support and connection; and the whole device is in through connection with another installation platform via the dovetail groove fixation platform. The auxiliary support device can solve the problems in placing the optical measurement system effectively, and satisfies measurement requirements in complex test conditions.