Abstract: A simple method of plotting the dispersion curve is proposed according to the character which dispersion curve is the real solution of dispersion function in essence. The reliability of the method was proved by the experiment which carried out on an aluminum plate of a thickness of 1.29 mm using a variable-angle probe of 2.5 MHz. The method was suitable for practical application by comparing the theoretical with experimental value of phase velocity,group velocity and excitation angle,and error analysis.