The effect of cirrus cloud on radiative transfer depends on its microphysical properties. The water content and number concentrations of ice particles in tropical anvil cirrus measured during the ACTIVE (Aerosol and Chemical Transport in Tropical Convection) field campaign (from November 2005 to February 2006 in Darwin area, Australia) are analyzed. Some advanced particle probes are utilized during this campaign, including Cloud Imaging Probe (CIP) and Cloud Particle Imager (CPI). A statistical analysis of the fifteen cases (only the slow phase of anvil cirrus with the height ranging from 9.7 to 14.9 km and temperature ranging from -70.4°C to -30.0°C, are considered) shows that the typical value of ice water content (IWC) is 10-2 g m-3, and the number concentrations of ice particles measured by CIP (>100mum) and CPI (>5mum), are 101 and 102 L-1, respectively. The changes in median of IWC in anvil cirri with temperature (or altitude) are examined and compared among different phases of Australian monsoon.