Abstract: Dynamic behaviors of beam structures with cracks are studied through the finite element method using dynamic stiffness matrix. A new beam element with a crack is proposed, and its dynamic stiffness matrix is derived by using the line-spring model in fracture mechanics. Numerical analysis is then carried out for both a cracked cantilever beam and a cracked frame structure, and the results agree well with the available experimental data, as well as those of analytical solutions. It is shown that the changes of crack location and crack length lead to the variation of both natural frequencies and mode shapes of a beam structure, and therefore should be taken into consideration in the dynamic analysis. The proposed element provides an efficient way and is well applicable for the analysis of a beam structure with multiple cracks, and good accuracy can be achieved.