Abstract: Characteristics of single-layer and multi-layer clouds including cloud amount, vertical structure of cloud, configuration of cloud type, and cloud water path in the Northern Hemisphere (0°-60°N) in boreal summer (June-July-August) are investigated based on measurements of the Cloud Profile Radar(CPR) during 2007-2010. The results indicate that the cloud amounts for single-, double-and triple-layer are 36.63%, 8.26%, and 1.40%, respectively. The high value areas of cloud amounts are consistent with convective regions with higher cloud top and thicker clouds, while the low value areas are mainly located over the subtropical high zone. The occurrence frequencies of cloud types show that the frequencies of cirrus, medium cloud and low cloud in single-layer cloud are similar, and the upper layers of multi-layer clouds mainly consist of cirrus, while the lower layers mainly consist of stratocumulus. Comparing frequencies of cloud types over ocean and land, the authors found that cirrus and stratocumulus occur more frequently over ocean than over land, while altostratus and altocumulus are emerging more frequently over land. The analyses also show that the values of cloud water path (ice water path and liquid water path) of single-layer clouds are the highest. In the multi-layer cloud, higher layers often have higher values of ice water path and lower values of liquid water path.