Statistical characteristics of cloud cover as functions of hours, months and seasons, the probability of cloud-free line-of-sight(P_CFLOS) as functions of hours and elevations in Hefei and southeast coastal areas of China were obtained by using Total Sky Imager 880. In Hefei, year-averaged cloud cover is more at noon,less in the morning and at dusk. The cloud cover distribution in southeast coastal areas are contrary to those in Hefei. In Hefei, the cloud cover in spring or summer is usually larger than that in autumn or winter.Month-averaged cloud cover in Hefei is 50%～80%, while 40%～55% in southeast coastal area. Maximum season-averaged P_CFLOS in Hefei is less than 0.35, while month-averaged P_CFLOS in southeast coastal area is up to 0.7.