Abstract: Based on the principle of Acoustic Elasticity, residual stress can be measured by ultrasonic method. The existing ultrasonic stress measurement is based on the idea of “single transmission and single receiving” . The single measurement can only measure the force in one direction, so the multi-direction stress measurement must be realized by the combination of multiple probes or the movement of one probe many times, the detection efficiency is low and the stress concentration can not be accurately detected. Testing, obtaining the working stress and residual stress at a smaller scale are the basis of accurate life evaluation. In order to meet the requirements of Life Assessment and higher resolution of residual stress measurement, an ultrasonic method of welding residual stress measurement based on array algorithm is proposed in this paper, by comparing the stress measured value sequence with the stress calculated value sequence, the optimal coefficient sequence is obtained and the optimal stress distribution curve is obtained.