The Moderate-Resolution Image Spectroradiometer (MODIS) and the Atmospheric Infrared Sounder (AIRS) measurements form the Earth Observing System’s (EOS) Aqua satellite enable global monitoring of the distribution of clouds during day and night. MODIS is able to provide at high spatial resolution (1~5km) the cloud mask, surface and cloud type, cloud phase, cloud-top pressure (CTP), effective cloud amount (ECA), cloud particle size (CPS), and cloud water path (CWP). AIRS is enable to provide CTP, ECA, CPS and CWP within the AIRS footprint with good accuracy using its greatly enhanced hyperspectal remote sensing capability. The blended MODIS/AIRS system offers the opportunity for cloud parameters improved over those possible from either system alone. The one-dimensional variational (1DVAR) and minimum residual (MR) methodologies (Li et al., 2004a; 2004b) are used to retrieve the CPS and COT from AIRS longwave window region cloudy radiance measurement. The results from 1DVAR are compared with the operational MODIS products and the AIRS alone cloud microphysical property retrieval, to demonstrate the advantage of blended MODIS cloud products and AIRS radiance measurements for optimal cloud parameter retrieval. Case study on Hurricane Isabel were used for comparison; results show that MODIS+AIRS 1DVAR provides an efficient way for cloud microphysical property retrieval during the day while the AIRS alone MR gives an option for the retrievals during the night.