Abstract: Compared and analyzed with the existing residual stress measuring techniques, an ultrasonic stress measuring technology based on the critical refracted longitudinal (LCR) wave was put forward and used to measure the stress. An ultrasonic stress measuring system based on the LCR wave, which adopted the mode of “one sending and two receiving”, was set up to measure and analyze the stress. The stress of circular flat-plate 5％Cr was tested with the ultrasonic stress measurement method and other two mature methods (X-ray diffraction and pin hole method) respectively. Contrasted three measuring results, it showed the ultrasonic stress measuring method based on the critical refracted longitudinal wave could be used to measure the stress of roller.