Abstract: The relationship between surface stress and laser-generated surface wave velocity of Q235 steel was studied by self-developed laser ultrasonic detector based on piezoelectric sensor with the help of the acoustoelasticity theory, and was compared with experiment results tested by surface wave piezoelectric probe. The relationship between surface stress and laser-generated surface wave velocity of cast iron brake disc was obtained by the detector. The residual stresses at different positions of the cast iron brake disc were detected by laser-generated surface wave technique and compared with that measured by X-ray stress analyzer. The results show that the acoustoelasticity coefficient of Q235 steel detected by laser-generated surface wave technique was 1.02×10^-5 MPa^-1, and was very close to that measured by surface wave piezoelectric probe. The stresses at different positions of the cast iron brake disc measured by laser-generated surface wave technique and X-ray stress technique were all compressive stress. The values of the stesses by the two techniques were different, but the stresses had the same trend.