The warm-season precipitation changes in arid and semi-arid areas over Northern China were ana-lyzed with monthly precipitation data from 756 stations in China from 1951 to 2011. The results indicated that the precipitation of arid and semi-arid areas showed an opposite trend in the recent 60 years. The warm-season precipitation increased overall in arid areas with 0.27 mm/a and decreased in semi-arid areas with 0.80 mm/a. The difference existed mainly because the two regions were controlled by different circulation systems, that is, the arid area by westerlies and semi-arid area by monsoons. A composite analysis of atmospheric circulation in these two areas for years with more (less) precipitation showed that, when westerly flow was strong and was southward, the water vapor of the Black Sea, the Caspian Sea and Lake Balkhash was carried to the arid region, conducive to the precipitation thereof, and vice versa. When the East Asian summer monsoon was strong and the water vapor was going westward to central Gansu (105oE), and northward to the entire north and northeast China, the precipitation of semi-arid areas increased, and vice versa.