The invention discloses a mechanical structure of an indoor building profile installation robot. The mechanical structure comprises a base, a mechanical arm and a mounting end. The mechanical arm is composed of three sets of connecting rods in series. Each set of connecting rods is connected with the last set by a connecting rod in a hinged mode, a rotating driving force is provided by a hydraulicoil cylinder in a both-end hinged mode, the set of connecting rods at the top is composed of three connecting rods and hinged to the mounting end through a tail end hinged part, and it can be ensuredthat the mounting end performs translational motion in the up-and-down and front-rear direction when the mechanical arm moves. The mechanical structure of the robot cooperates with a control system and a driving device, the problem of large-size high-weight building profile installation under the conditions of height and working space limitation can be solved, the mechanical structure can be usedfor transport installation of building profiles in indoor and outdoor low-altitude environments such as a workshop and a workshop, the operation is simple, the running is smooth and saves labor, andthe mechanical structure is efficient and safe.