Abstract: The dynamic experiment of a non-bonded full pre-stressed concrete beam was carried out. The experimental results indicated that the frequencies of the beam increase with the prestressing force increases. The results were different from those of dynamic characteristics which were put forward by Clough about isotropic material beam subjected compressive axial force. The reason is that the beams are considered as isotropic, homogeneous and linear elastic material by the traditional analysis method. Thusly, it requests more accurate results in analysis of pre-stressed concrete frequencies. The constitutive mode of pre-stressed concrete member is analyzed based on microstructure of concrete. Meanwhile, the bending deformation stiffness of the beam is regarded as the sum of the equivalent stiffness of the prestressing tendon and the concrete beam. The orthotropic linear elastic mode is used to analyze and calculate the relation between the dynamic frequency and prestressing force of the concrete beam. The analysis values agree with the test results well. And the beam that Saiidi et al. studied is analyzed by the proposed method. The results are accorded greatly with the experimental data.