By use of the pentad precipitation data from 23 stations in Guangdong Province during the second rainy season (July to September) from 1961 to 2006， the characteristics of the spatialtemporal distribution and variation of precipitation are analyzed in terms of the Precipitation Concentration Degree (PCD) and Precipitation Concentration Period (PCP). The results show that PCD and PCP can reflect well the spatialtemporal distribution of the precipitation. There was a weak descending trend and various periodic variations at interannual and decade scales in PCD in Guangdong Province during the second rainy season. The spatial distribution of PCD shows the characteristic of decreasing from north to south successively. PCD had a uneven distribution， more concentrative over the central part of Guangdong in rainy years than dry years. PCPs in rainy years were smaller than those in dry years. By the empirical orthogonal function (EOF) method， the first eigenvector of PCD shows the characteristic of identical increasing trend over the province， with the contours being northeastsouthwest oriented， but the second eigenvector is opposite from the east to the west. The circulation field analysis shows that in the high PCD years， the northern China was often controlled by high pressure systems at 1000 hPa and 500 hPa high fields， and there was usually a positive anomaly center in the height field， while the high pressure often extended southward， which converged with the warm and wet air， leading to strong precipitation.