The goal of this project is to validate monitoring data quality of the aerosol supersite (herein supersite) of the Taiwan Environmental Protection Administration (TEPA) by implementing quality assurance (QA) procedure. To achieve this goal, a regular site inspection at each monitoring station is performed every month and every season. The QA inspection is also applied to the Loon-Bay site moved from the Chiao-Tou site. To improve data quality, this project participates in every supersite maintenance and operation review meeting on monthly and seasonal bases. Meanwhile, an assessment on the weekly data report submitted by the maintenance company has been filed consecutively to the TEPA since April. In addition, a consistent QA procedure was accomplished and applied to all supersites plus the method for eliminating erroneous and unrealistic data further improve the data quality. The data acquisition rate in common instruments across all sites is the highest at 98.6% for PM2.5 aerosol mass monitor and the lowest at 66.3% for aerosol carbon analyzer. The four aerosol size spectrometers at the Hsin-Chuan and the Foo-Yin core sites performed badly this year. The data acquisition rate of micron-particle size spectrometer was only 43.3% and the nano-particle size spectrometer was 77.0% at the Hsin-Chuan site. In contrast, the data acquisition rate of micron-particle size spectrometer was 71.1%, while the nano-particle size spectrometer was increased to 69.7%, after replacing with a new data-conversion-software at the Foo-Yin site. Through a stringent and effective QA mechanism, significant problems such as the leakage of aerosol carbon analyzers, the worn-out of chopper glass of an Integrating Nephelometer, the size shifting of a micron-particle size spectrometer were thus discovered and fixed. In summary, the effectiveness of monitoring data quality is assured and the life of instruments is extended due to the efforts contributed from this project.