Abstract: In order to study the effects of cloud cover on climatic factors in Tianshui, based on the data of cloud mount in 1951-2010 in 7 weather stations in Tianshui, the relationship between cloud amount and its interrelated climatic factors had been analyzed. The results showed: the number of all level rain days, precipitation and amount of cloud were notability correlation. It also indicated that: the precipitation varied with cloud amount in which the amount of cloud increased by 10%, with the annual precipitation increased by 160 mm, spring precipitation increased by 23 mm, summer precipitation increased by 79 mm, autumn precipitation increased by 39 mm and winter precipitation increased by 3 mm. The correlation between cloud amount and temperature showed periodical change in which cloud amount increased by 10% with mean temperature decreased by 0.7℃ and 0.5℃ respectively in spring and summer, but there was no correlation between cloud and mean winter and autumn temperature. The sunshine hours was seriously influenced by cloud amount in which cloud amount increased by 10%, with the sunshine hours decreased by 104 h in spring, 92 h in summer, 85 h in autumn and 65 h in winter. There was positive correlative between mean cloud amount and relative humidity in which cloud amount increased by 10%, with the relative humidity increased by 4% in summer, by 3% in spring and autumn, by 2% in winter.