In order to study the properties of the carbon nanotube(CNT) cathode with intense pulsed emission, the outgassing property of cathode is investigated on the 2MeV linear induction accelerator(LIA) injector. Results show that the cathode has a capability of desorbing gases from the CNT cathode under pulsed high voltage. The outgassing plays an important role in the formation of the cathode plasma. The amounts of outgassing for the several experiments are estimated to be 0.081.12PaL, the corresponding ratios between outgassing amount and electron number are roughly calculated to be in a range of 254203atoms/e- by numerical integral of pressure, showing that the cathode plasma is weakly ionized. The relationship between diode voltage, emission current density, outgassing amount, and the outgassing molecule number per electron are analyzed.