Abstract: Based on acoustic elastic theory, this paper analyzes the relationship between stress and elastic wave velocity, analyzes the physical significance of acoustoelastic equation, summarizes the state of the art of residual stress testing based on LCR wave at home and abroad, advances some unfathomed problems and gives solutions. A new subsurface stress measurement method and a biaxial tensile test specimen are designed specific to the problem. And at the same time, the simulation of specimen is carried out in order to explore the distribution of stress. The simulation results illustrate that the method of coefficient calibration under the bidirectional loading is feasible.