We　utilized　a　coherent　terahertz　time-domain　spectroscopy　system　to　measure　the　dynamic　conductivity　of　an　InAs　two-dimensional　electron　gas.　Based　on　the　theoretical　transmission　analysis,　the　real　and　imaginary　parts　of　the　complex　conductivity　of　the　sample　were　extracted　from　the　transmitted　terahertz　time-domain　waveforms.　We　also　measured　the　sample　at　low　temperatures　and　fitted　the　real　and　imaginary　parts　of　the　conductivity　with　the　Drude　model　to　extract　its　densities　and　mobilities.　The　dominant　scattering　mechanisms　are　discussed　according　to　the　temperature　dependence　of　the　extracted　densities　and　mobilities.　©　2017　Elsevier　B.V.