Abstract: In order to make up for the shortcoming of the traditional continuous aerosol monitoring technology in the detection ability and response speed of continuous 239Pu aerosol activity concentration monitoring in the reprocessing plant, the continuous 239Pu aerosol activity concentration monitoring technology based on ICPMS was studied. With the research of aerosol direct sampling method, ICPMS continuous measurement quantitative method and 238U interference to the system, a continuous 239Pu aerosol activity concentration monitoring technology based on ICPMS, aerosol direct sampling device and membrane desolvation nebulizer was established. The decision threshold and detection limit of this system for measuring 239Pu aerosol activity concentration was calculated according to the ISO 11929(2019), which are 1.24×10-5 Bq/m3 and 2.48×10-5 Bq/m3 with 1 min measurement. Detection performance of this system is better than those of continuous α monitors based on planar implanted passivated silicon (PIPS) and much lower than the derived air concentration (DAC) of 239Pu. It is proved that this technology can provide efficiently technical support for continuous 239Pu aerosol activity concentration monitoring in related workplaces.