The utility model relates to a substation, especially to an indoor overhead structure for a substation. The utility model provides the technical scheme as follows: the indoor overhead structure for the substation comprises an annular wall, a foundation ground layer positioned at the bottom of the annular wall and a floor plate which is arranged parallel to the foundation ground layer, is erected on the annular wall and is used for placing equipment. A ground beam which is erected with the annular wall is arranged on the foundation ground layer. A secondary beam is disposed between the ground beam and the floor plate. The secondary beam is arranged on the annular wall. The floor plate is arranged on the secondary beam. The secondary beam and the ground beam are in contact connection through masonry bearers. Load on the floor plate is transferred to the ground beam through the secondary beam and the masonry bearers. There are spaces in the vertical direction among the masonry bearers. The spaces are cable laying spaces and cable trenches. By the above technical scheme, a substation's indoor overhead structure which has advantages of cost reduction, manufacturing convenience and simple structure is provided.