An automatic cavity adjustment system was established to improve the quality of laser gyro cavity adjustment and to overcome the drawbacks of manual detection such as low efficiency and low anti-interference capacity. According to the process of the cavity adjustment, a multi-sensor information fusion architecture was established by a CCD camera and a photomultiplier. A detection method of laser gyro cavity adjustment was proposed based on the D-S evidence theory. By analysis and calculation of the signals detected by the CCD camera and the photomultiplier, the center coordinate difference between facula and diaphragm and the loss value of the laser gyro were obtained and the evaluation function for each cavity adjustment result was deduced by these data. Furthermore, the qualified and unqualified belief functions of the cavity adjustment were obtained, respectively, and the quality of the cavity adjustment was verified based on the maximum support rule. The experimental result indicates that the accuracy of the detection method based on D-S evidence theory is 91.14%, which improves the quality of cavity adjustment effectively and validates the feasibility of the proposed method.