The invention relates to a triangular stereoscopic measuring instrument which can be used to measure the distance and the angle within a narrow range in power engineering and belongs to the technical field of measuring instruments. The triangular stereoscopic measuring instrument comprises a fixed disk and three support rods of the same height, the support rods are fixed to the bottom of the fixed disk, the top of the fixed disk is provided with a gradiometer, the bottom of the fixed disk is provide with a fixed guide rail and a movable guide rail, the bottoms of the fixed guide rail and the movable guide rail are provided with guide rail grooves respectively, one end of the movable guide rail is mounted in the fixed guide rail and can move to and fro in the groove of the fixed guide rail, the groove of the fixed guide rail is internally provided with two connecting balls, the two connecting balls are respectively placed at the two ends of the movable guide rail, the groove of the movable guide rail is provided with another connecting ball which can slide in the groove of the movable guide rail, and the three connecting balls are fixed to the support rods respectively. The triangular stereoscopic measuring instrument of the invention can be applied to power engineering, is simple in operation, high in measuring precision and capable of measure the distance and the angle.