Ethylenediaminetetraacetic acid (EDTA) was decomposed by supercritical water oxidation (SCWO) in a tubular plug-flow reactor. The effect of the oxidant amount on the decomposition rate and efficiency was more significant at lower temperature. Also, excess oxidant played a key role in decreasing the activation energy for EDTA decomposition as CODCr. The nitrogen from EDTA was found to transform into NO3--N by thermal decomposition, while a portion of the nitrogen of EDTA and NO3--N was transformed into NH4+-N and finally converted to N-2 gas in the SCWO process. The decomposition kinetics of EDTA as CODCr in the SCWO process was described by a global rate expression.