Abstract: A technique for fast analysis of plutonium in airborne aerosol was developed with directly sampling ICP-MS in this laboratory. And the Pu-242 aerosol particle addition calibration method was established. The nebulized Pu-242 solution aerosol was quantitatively mixed with the airborne aerosol and then introduced into ICP-MS. The results show that the detection limit for Pu-239 concentration is down to 1.4×10^－6 Bq·L^－3. The airborne aerosol sample after through a high efficiency particulate air (HEPA) filter with six stages (efficiency per stage 99.95%) was analyzed using this technique, the plutonium concentration determined is 3×10^－4 Bq·L^－3. However plutonium could not be detected when sampling using HEPA filter at same situation, airborne aerosol also could not be detected at same situation with Condensation Particle Counter (CPC). This result shows there were some tiny plutonium particulates which passed through the six stages HEPA filter with airflow and could not be collected by the HEPA filter