Abstract: A VSS RGA10 mass spectrometer in a typical configuration for Ar isotopic analyses has a resolution of 85~100 and a sensitivity of 1.47×10 -2 A/Pa. Recently, The ion sources and the sample preparation system have been improved. 38Ar spike reservoir, control software and data acquisition system has put on the RGA10 mass spectrometer. The sensitivity has increased from 1.47×10 -2 A/Pa to 5.77×10 -2 A/Pa. The total system vacuum has raised from 2.6×10 -4 Pa to 1.6×10 -6 Pa. With the new modifications of the RGA10, mass spectrometer is better than ever. The precision of determination of Ar isotopic is better than 1%. The study shows that the measurement efficiency of instrument have been improved significantly compared with previous data of K-Ar aging and Ar-Ar total fusion aging. Their applications are discussed in this paper.