The invention discloses an auxiliary detection vehicle for advanced forecasting of a highway tunnel geological radar. The auxiliary detection vehicle comprises an operating bench, a first mobile unit, a second mobile unit, a connecting rod unit, a balancing unit and a radar antenna. The first mobile unit is arranged above the operating bench and the second mobile unit is arranged below the operating bench; the moving directions of the first mobile unit and the second mobile unit are perpendicular to each other; and a radar antenna is connected with the second mobile unit by a connecting rod. On the basis of sliding of the first mobile unit and lifting of a first connecting rod, complete coverage of a tunnel face range can be realized, so that detection points can be distributed in the face range uniformly; with a sliding guide rail, stable movement of the detection vehicle during the detection process is guaranteed and the accuracy of the detection result is ensured; tight contact between the antenna and the tunnel face surrounding rock during the detection process is guaranteed based on movement of the second mobile unit and elastic compression of a second connecting rod, so that an objective of protecting an instrument and a detection vehicle can be achieved.