Abstract: The acoustoelasticity equations were deduced by means of the infinitesimal wave propagation in a deformed isotropic elastic material.The equations were simplified in the longitudinal critically refracted waves expression.Ultrasonic stress measurement installation was established with a special transducer and an oscillograph with special higher digitizer board.Longitudinal critically refracted wave which is sensitive to stress variation was selected as the measuring wave.Longitudinal residual stress gradient of 2219 aluminum alloy was obtained in the ultrasonic travel time change expression formal.The tendency was compared with the numerical simulation results obtained by Marc software.Preparation for longitudinal residual stress field of 2219 aluminum alloy butt-welded steel plate was made.