By applying rotated empirical orthogonal function (REOF) analysis on dryness/wetness (DW) series from 1470 to 1999 at 100 selected stations over the eastern part of China, defined by the large contours of the seven REOF modes, 7 dryness/wetness active centers are identified: Northeast China, northern North China, southern North China, Northwest China, the middle and lower Yangtze River valley, South China and Southwest China. The temporal variations of regional dryness/wetness for monsoon boundary zone in northern China are investigated on the basis of the regional division of dryness/wetness. Dryness occurred fairly frequently in Northeast China, southern North China and Northwest China in the 16th century and the first half of the 17th century. In the 18th and 19th centuries, the occurrence of dryness is more frequent in northern North China, but the occurrence of wetness is more frequent in Northeast China, dryness/wetness occurred alternately in southern North China and Northwest China. The changes of dryness/wetness jumped from wetness to dryness in northern North China and southern North China during the late 19th century and the early 20th century respectively. Dryness had kept still in two divisions.The study shows extreme dryness has similar trend, which increased at both ends and less in the middle in Northeast China, northern North China and Northwest China during the last 530 years. But it is a frequently occurring area in southern North China.