In roundness measurement, filtration is a basic step before the evaluation of the roundness deviation parameters. Current widely used phase correct 2RC filter and Gaussian filter are not robust against measurement outliers. This paper introduces a robust roundness filtration technology which is based on the robust Gaussian regression filter. Mathematical solution and its algorithms calculated in time domain and in frequency domain are both presented. Both simulated and practical roundness profile data have been used to test the speed and accuracy of the algorithm. Results show that with the proposed robust algorithm, the outlier’s influence on the roundness deviation parameters can be reduced significantly, while still keep the similar transmission characteristics with the standard Gaussian filter very well. And also, the difference between the results of the two presented algorithms is very tiny and negligible.