The paper presents a dynamic computational model and field test for analyzing the relationship between the rail natural frequencies and the longitudinal temperature stress by means of the finite element method. The essay use the infinite Timoshenko beam as the plane model to simulate continuous welded rail track structure and the rail model by means of the finite element method in order to its unit as a division of space elastomer. The test uses vertical incentive and horizontal incentive to encourage continuous welded rail track structure to get the rail natural frequencies. The measured data and the result of finite element analysis are compared, finds the results are consistent. The paper not only investigates the relationship between the rail’s dynamic characteristics and the longitudinal stress, but also provides a feasible method for test longitudinal stress of continuous welded rail track.