Gage repeatability and reproducibility (Gage R&R) test is a statistic quality control method for evaluating the precision of a measurement system. By evaluating large amount of measurements performed by several operators on certain number of parts for several times, the method estimates a measurement system on its repeatability, reproducibility, part to part variation, and variation of the total system. The residual stress measurement system evaluated in this study is a Bruker General Area Detector Diffraction Systems (GADDS). Gage R&R test shows that the overall measurement error is 6% or less. The repeatability error of the system is 5.5% or less, and the reproducibility error is 2.3% or less.