[Purposes] Surface damage is prone to occur during the process of laser machining of bearing steel. Therefore, a method of characterizing the degree of damage in laser machined bearing steel using nonlinear ultrasonic surface waves are investigated. [Methods]Different laser processing parameters are employed to carry out surface treatment of GCr15 bearing steel specimens, resulting in various degrees of surface damage. A nonlinear ultrasonic surface wave detection system is established to measure the nonlinear coefficient of the ultrasonic surface wave of the bearing steel at different levels of damage, which also analyzed the relationship between the degree of damage and the nonlinear coefficient of the surface wave. [Findings]After laser surface treatment, the nonlinear coefficient of the surface wave on the bearing steel increased, and it is positively correlated with the degree of damage. When severe damage occurred, the change in the nonlinear coefficient became more drastic. Comparing with traditional linear acoustic parameters, the nonlinear coefficient of the surface wave is more sensitive to the degree of surface damage on the bearing steel. After normalizing conventional linear and nonlinear acoustic parameters, it is discovered that the wave velocity is hardly affected by the surface damage level, and the rate of change in the sound attenuation coefficient is only 0.25 with respect to the degree of damage. However, the rate of change in the nonlinear coefficient of the surface wave is 0.98 with respect to the degree of damage. [Conclusions] The use of the nonlinear coefficient of the surface wave can effectively characterize the degree of laser damage on the surface of the bearing steel.