Abstract: The samples including NBS U010, concentrated nitric acid solution of 233U(IRMM-040a)were determined by Finnigan MAT 262 thermal ionization mass spectrometry. The isotopic ratios in low abundance uranium included 234U, 235U, 236U were determined by RPQ-IC collector system. The results were compared with data obtained from Faraday cup. The calibration of RPQ yields by deflexion was described. The result shows that the determination datun is in the range of error, the result obtained from RPQ-IC is 0.14% higher than that from Faraday cup, the inner precision and outer precision from the determination of isotopic ratios of low abundance uranium by RPQ-IC collector system are higher than from Faraday cup. The change of RPQ yields is very significant.