The accuracy of the Standard Positioning Service of GPS has greatly improved after the termination of Selective Availability. Based on GPS observations from permanent GPS-fixed stations, the actual accuracy of GPS without SA is analyzed. For Station NCTU, the local geodetic coordinates are computed with the C/A code pseudo-ranges, and then transformed into a local grid system with Trans-Mercator projection. From 77984 single epoch observations collected in twenty-nine days, the 95% accuracy is found to be ΔE : 17.6544m, ΔN : 11.8236m, ΔH : 31.8018m. For five selected UNAVCO stations, the axes of error ellipsoid are computed.