The infrared image of the sky near the ground is analyzed statistically.The mean of gray level, variance, horizontal and vertical scanning line, histogram of long-wave(8～12 μm)infrared images of the sky near the ground are analyzed. The images consist of 100% sunny, 100% cloudy, cloudy and night. Result about the analysis is also given. The relation between gray level mean and atmospheric temperature is linear. The variance of 100% cloudy sky image is small. Gray level linearly changes in vertical scanning line and keeps stable in horizontal scanning line. The histogram of image depends on the weather and time.