Abstract: Dynamic characteristic of a curved beam is an important part in curved beam structure design. In order to study the vibration characteristics of pre-stressed circular curved beams, we take an infinitesimal segment of a pre-stressed curved beam as a case, and by considering the influence of pre-forcing on bending moment, derive the vibration differential equations of arc-curved beam based on d′Alembert principle. The formula for the first order natural vibration frequency in plane of a pre-stressed simply supported circular curved beam is obtained. Finally, by comparing with numerical results of FEM, the proposed analytical formula is verified.