The utility model relates to a circular ring-shaped flat jack which is applied to a prestressed concrete tunnel and is provided with a circular ring-shaped body. The circular ring-shaped body is provided with a cavity into which a pressure applying medium can be injected; the circular ring-shaped body is a hollow circular ring-shaped pressure device capable of radially applying uniformly distributed pressure stress to the outside of lined concrete along a circular ring by the pressure applying medium through limited radial displacement. The circular ring-shaped flat jack adopted by the utility model omits use of prestressing steel in the prior art and is convenient to construct; moreover, the prestress degree is improved and a concrete lined layer has no tensile stress phenomenon, so that longitudinal cracks and the internal water seepage phenomenon are prevented.