The invention relates to an inner tensioning pre-stressed concrete single-layer variable section plate box-type structure of a building. A variable section plate is arranged in the direction parallel to the section of the structure to form a box-type section, the span range of the variable section plate is 7 to 36 meters, prestressed ribs are arranged in the variable section plate, and tensioning grooves are reserved on the plate side faces which have low stress and facilitate construction in the structure; and when concrete reaches the specified strength, the segments of the same prestressed rib bundle are sequentially connected end to end through middle anchors at the tensioning grooves and tensioned, and then the tensioning grooves are plugged. The structure is characterized in that the tensioning grooves are reserved on the plate side faces which have low stress and facilitate construction in the structure, and the prestressed ribs are connected through the middle anchors and tensioned. The structure has the advantages that when the ends of a structural member do not have tensioning and anchoring conditions, prestressed tensioning anchorage can be realized, high comfort degree, using performance and structural performance can be provided, and the structure is particularly suitable to be used as an underground heavy-duty and large-span single-layer framework box-type structure.