Abstract: There has been relatively less research on the physical properties of mid-level clouds. In this study, the CloudSat and CALIPSO satellite cloud data from Jan 2007 to Dec 2010 for the North China (area A1), Sea of Japan (area A2), and the Pacific (area A3) was used to analyze the physical characteristics of mid-level clouds (As and Ac). The occurrences of middle level clouds are around 1/3 over all the three areas. The As occurs higher (4-8 km) than the Ac (3.5-5.5 km). The average size of mid-level clouds increases from land to sea. Temperature in the middle troposphere supports the condition for mid-level clouds to contain both ice and supercooled liquid particles. Our statistical results indicate that ice particles dominate in As, while the proportions of liquid and ice particles are similar in Ac. The IER (Ice Effective Radius) of As and Ac varied from 35 to 80 μm and the height and IER of As and Ac ice particles were negatively correlated. The LER (Liquid Effective Radius) of As is highly positively correlated with height, but this correlation is weakened in Ac. The LER values in Ac and As mainly range between 5-15 μm. The IWC and LWC of As and Ac show no obvious correlation with height.