The invention relates to a construction of a subway shield shaft single-layer main body structure and belongs to the field of subway construction. The process is characterized by including: only the third underground layer main body structure of the shield main body structure is constructed, the main body structures of the underground first layer and the underground second layer are replaced by cast-in-situ ring girders. The size of each cast-in-situ ring girder is 800*80mm. The ring girders are connected through embedded steel bars and fender posts. Monitoring measurement is enhanced during shield hoisting. By the construction process, the construction period of the whole project is shortened by 20 days while construction safety is guaranteed, and about 30% of construction cost is saved.