In order to measure the stress birefringence of heat strengthened glass quickly and accurately, and to monitor the product quality in real time, the automatic stress birefringence measurement technology of heat strengthened glass based on laser feedback was studied by combining the semi-classical theory and the three-mirror cavity theory model. The measuring equipment was composed of precision optical elements and motion platform, and the main stress direction of the sample was automatically judged by calculating the duty cycle of the low level of polarized light. The measurement efficiency was improved; The fluctuation range of output voltage was controlled within a narrow range by reducing the gradient of input voltage change, which improves displacement stability of piezoelectric ceramics. The experimental results show that the value of the stress birefringence of the sample is determined by the position of the flipping point in a polarization flipping period on the tuning curve. The maximum deviation of multiple measurements is 6.1nm/cm and the standard deviation is less than 2.0nm/cm in multiple measurements. Such technology has the characteristics of short measurement period, high precision and good repeatability, which is suitable for practical production.