Abstract: Shaanxi Province is the climate sensitive region of China, locating at northwest inland. The probability distribution of water cloud, cloud-top height, optical thickness and the effective radius of cloud are analyzed by using MYD06-L2 of MODIS cloud product to understand the property of water cloud over Shaanxi. The results were concluded as follows: (1) Single peak was obtained for probability distribution pattern of water cloud and reached the top at November, while the lowest at May. Moreover, the maximum and minimum appearance probabilities were observed at autumn and spring. (2) The probability distribution of water cloud-top height produced significant change in July and September, and from April to May, the water could-top height mean value reached the maximum and from December to February the minimum mean value appeared, and specially that of July and August showed distinct form. (3) It was found that the probability distributions of the effective radius of cloud particle are similar from October to May the next year, while obvious differences existed from June to September. The maximum and minimum average appeared from June to August and in November, respectively. (4) The water cloud with optical thickness ranging 0$\sim$5, had a higher probability from October to May the next year and reached the top from December to February the next year. Yet, water cloud with optical thickness ranging 5$\sim$10 performed different. The higher probability existed from May to October, and reached the top from July to August. Additionally, the maximum and minimum of optical thickness occure from September to November and July to August, respectively.

Key words: water cloud, cloud-top height, effective radius of cloud particle, cloud optical thickness, probability distribution