In order to eliminate the signal noises and restrain the residual errors in the beam-coupling assembly process of ring laser gyroscopes, a robust estimation based on Gaussian filtering algorithm is presented. According to the signal characteristics in the beam-coupling assembly process, IGGIII robust estimation and eHuber robust estimation are used to deal with the signals. And the signal processing results between the two robust estimation methods and traditional Gaussian filtering method are compared and analyzed. By using iterative algorithm, proportion error, mean absolute error, root mean square error and signal-to-noise ratio are obtained. Experimental results show that IGGIII robust Gaussian filter can improve the robust performance of traditional Gaussian filtering and the signal errors in the beam-coupling assembly process are filtered effectively, and the signals after filtering are closest to the real signals. Therefore, the results validate the robust Gaussian filtering method.