A new method based on laser ultrasonic was proposed to survey welding stress distributions on the material surface according to the acoustoelastic principle, The high frequency Rayleigh waves excited by the Nd:YAG pulsed laser were used to measure the welding stress and picked up by a nonlinear interferometer. A serial of ultrasonic pulsed signals can be detected by the interferometer through changing the distance between fixed detecting point and ultrasonic source point by the scanning of the laser source. The waveform cross-correlation technique was applied to compute the propagation time delay of the adjacent Rayleigh waves, and the propagation velocity of the Rayleigh waves was obtained, by which the stress value was figured out via acoustoelastic relation. The residual stress distribution can be measured around welded joint while the laser source scans around the welded joint. This experimental installation was utilized to test the welding stress on the surface of a welded aluminum plate and the stress distribution was measured. The experimental results indicate that this method can scan over the specimen surface and measure the welding stress quickly, which make it have potential in the non-destructive evaluation of the surface welding stress distribution.