Abstract: The effective radius of cloud particles is a crucial indicator in cloud microphysics. Thus, accurately determining the distribution characteristics of effective particle radius is imperative for cloud formation analysis, precipitation and severe weather forecasting, and earth−air radiation budget. From the measurements of the visible and infrared scanner (VIRS) carried by the tropical rainfall measuring mission (TRMM), the spatial distribution and profile characteristics of the effective particle radius are examined for the summer of June–August 1998–2012. The results reveal that the effective particle radius is not uniformly distributed in space. The particle scales are 5–30 µm, while the local scales can reach more than 30 µm. Moreover, the particles over the ocean have larger effective radii than those over the land. The standard deviation is mostly 2–10 µm but can reach more than 10 µm in some regions. The profile distribution of the effective particle radius in different regions shows that the effective particle radius increases first and then decreases with decreasing brightness temperature. For the small effective particle radius, the profile over the ocean is larger than that over the land, and the profile in the northern subtropical zone is larger than that in the southern subtropical zone. For the large effective particle radius, the difference in profile among different regions is small. The standard deviation profile of the effective particle radius presents that the maximum standard deviations of small, moderate, and large particles are located at the ice cloud, mixing cloud, and water cloud regions, respectively. This study provides an observation basis for the model to simulate the distribution characteristics of the effective radius of cloud particles in tropical and subtropical regions.