Based on the linear elastic theory, the in-plane free vibration differential equations for isotropic and thin circular annular plates are derived. Using differential quadrature method, the dimensionless frequencies of in-plane free vibration of circular annular plates are investigated. The application of DQM in this paper have illustrated the method was validated and accurate by comparison of previously reported results with it. Finally, the influence for dimensionless frequency owing to inside and outside radius ratio of circular annular disk under the four different boundary conditions is considered.