The rotating bending and the inverse rotating bending are the two different forms of fatigue fracture. Some fracture problems for middle carbon steel in extra-low rotating bending fatigue loading are studied in this paper. The experiments of inverse rotating bending fatigue have been made in special equipment designed by us. Several problems, the relations of the cycle times of fracture and the strain amplitude near notch tip to the deflection, the relations of the depth of crack propagation to the cycle times of fracture, are discussed through the experiments. The effects of depth and tip radius of notch to the cycle times of fracture are studied also in this paper. The suitable parameters of inverse rotating bending fatigue fracture model for middle-carbon steel in extra-low cycle times has been proposed.