A method based on thermo-elastic excitation of ultrasonic waves generated by laser at the surface of a cylinder is presented. The propagation rules of head waves at the aluminum cylinders with different radii or different thicknesses are researched. The propagation characteristics of head waves are analyzed. The numerical results show that head waves are generated at the certain range (critical angle) in the body, and then spread along the straight line at a speed slightly larger than that of the Rayleigh waves. In the propagation process, the head waves move away from the Rayleigh waves and approximate longitudinal waves. The sine values of the critical angle (at the maximum amplitude) are almost equal to the wave-velocity ratios of the Rayleigh wave and longitudinal-wave in the cylinder. At the interface, a part of the head wave escapes from the body and spreads along the circumference with a rapid attenuation, while the other part of the head wave has a reflection at the interface with a small attenuation.