Abstract: The single arc bellows diaphragm is regarded as the combined structure of a circular plate with initial deflection by the method of simulated shell. Based on nonlinear large deflection bending theory, the nonlinear large deformation of a single circular diaphragm is analyzed. Taking the maximum deflection of the circular part of the diaphragm as a perturbation parameter and using modified iteration method of theory of plates and shells, the nonlinear large deformation of a single circular arc bellows diaphragm with one end fixed and another end free is solved. Under boundary conditions and continuity conditions, quadratic nonlinearity analytical solutions with higher accuracy are obtained. According to the vector height of the arc and the wavelength of the arc in a single circular arc bellows diaphragm, the characteristic curve of the maximum deflection of the arc is drawn. The characteristic curve is analyzed, the deflection of the diaphragm nonlinearly increases with the increase of the vector height of the single arc diaphragm, and the deflection of the diaphragm nonlinearly increases with the increase of the arc length of the single arc bellows diaphragm.