Accurate and rapid monitoring of 99Tc is crucial for the radiological risk assessment in nuclear emergency situations. However, accurate determination of 99Tc by ICP-MS is always hindered by the interferences of 98Mo and 99Ru. In this work, a rapid and accurate analytical method of 99Tc in seawater samples was established, and 185Re as a non-isotopic tracer was used for the monitoring of 99Tc yield in the whole procedure. TiCl3 was chosen as a reducing agent and co-precipitant for the 99Tc preconcentration. 98Mo and 99Ru were effectively removed using two TK200 resin columns under novel alkaline loading conditions, and the excellent decontamination factors (DFs) of 4.28 × 106 for Mo and 5.16 × 105 for Ru were achieved. Importantly, the interferences of 98Mo+ tailing, 99Ru+ and 98Mo1H+ can be efficiently suppressed using C2H4 as a new reaction gas for 99Tc measurement, and 98Mo1H+/98Mo+ of 1.31 × 10?7 was achieved at 0.28 mL/min C2H4-1.0 mL/min He. The overall decontamination factor of Ru reached 3.76 × 107, which are at least 2 orders of magnitude higher than that of the conventional methods. The detection limit of 3.18 pg/L (2.00 mBq/L) was obtained with a whole analytical time of 4 hours for 12 samples, which was suitable for the application of nuclear emergency. More importantly, this correction-free alternative method was found to accurately measure 99Tc by ICP-MS without any mathematical correction of 99Ru for the first time.