A developed calibration method of six-port junction is proposed, in which A dual-tone technique is used to produce multi-samples and more accurate results are achieved by use of the least-square method and excluding those samples which may cause bigger errors. A 0.9 similar to 5 GHz MIC six-port reflectometer was constructed and the Engen's robust calibration procedure was used for comparison. Eight test samples were used in the measurement For Engen's calibration procedure, the difference between the HP8510 and the six port reflectrometer is in the order of 0.3 dB/1.6 degrees for most cases, but at the boundary frequencies the biggest differences are 0.65 dB/2.60 degrees; while this method give the difference range between the UP8510 is less than 0.1 dB/1 degrees for most cases and a biggest error of 0.35 dB/1.7 degrees for boundary frequencies. This method can apparently increase the measure accuracy - especially at the boundary frequencies of six-port junction.