Disclosed are an above-ground over-limit settlement post-cast strip structure system and a construction method thereof. The construction method of the above-ground over-limit settlement post-cast strip structure system includes steps as follows: step 1, sealing a post-cast strip on a top slab of a basement for protection; step 2, constructing a main structure of a main building, a main structure of a skirt building, an external expansion structure of the main building and an external expansion structure of the skirt building, performing rib throwing treatment on girder and plate steel ribs of an over-limit settlement post-cast strip structure; step 3, building a frame body and templates of girders and plates of the over-limit settlement post-cast strip structure; step 4, constructing the girder and plate steel ribs of the over-limit settlement post-cast strip structure; step 5, pouring concrete of the over-limit settlement post-cast strip structure; step 6, maintaining the over-limit settlement post-cast strip structure. The above-ground over-limit settlement post-cast strip structure system and the construction method thereof solve the technical problems that girders can not be closed, building stability is poor, the girders can not be arched normally after being cut off, overall structure stress bearing is poor, templates and frame bodies are complex in connecting mode and difficult to operate, due to large differential settlement, and material is seriously wasted due to overstocking of materials such as the templates, steel pipes and the like, existing in a traditional post-cast strip construction method.