Abstract: Anomalous features of Asian summer monsoon and their influence on the continual torrential rain in South China in early summer of 2005 are analyzed. The results show that Southwest monsoon surges play a very important role in the rain band movement in Eastern China from the end of May to June. The South China Sea (SCS) summer monsoon doesn't start until the end of May (about three pentads later than normal) and leads to the obvious delay of the flood season in South China. From then on, Southwest monsoon over the Bay of Bengal moves mainly eastwards with smaller components towards the southeast part of Tibet Plateau than normal. At the same time, the western Pacific subtropical anticyclone (WPSA) is weaker and remains farther away from China mainland, and the cross-equatorial flow between 105°-115°E is weaker so that the northern component of the Southwest monsoon is also smaller. Meanwhile, East Asia trough is deeper and leads stronger cold air to China. All of these result in the Southwest monsoon main taining in south China and cause continual torrential rain there. Weaker Australia High is an important factor for the weaker cross-equatorial flow, and the weaker southward ITCZ and WPSA. Due to the stronger cold air over the large area from southern part of the Tibet to the northern India, the Indian monsoon breaks out late and marches slowly northwards so that the convection and the latent heat and the heat sources over southern part of Tibet Plateau and Bay of Bengal are obviously weaker than normal. The negative thermal feedback mechanism is conversely unfavorable for the northward marching of southwest monsoon. This is another important cause for the southwest monsoon and torrential rain's long-time staying in South China.