The extreme precipitation (EP) amount from April to July in Lake Poyang area exhibits significant quasi-periodic oscillations of 2-4 years, and its variance has remarkable ascendant trend. June EP amount in Lake Poyang area was abundant in 1998, while it decreased sharply in 2001, which only accounted for 13.5% of annual precipitation in 1998. Tlirough analyzing the difference of atmospheric circulation and moisture transport between the two periods, the results show that the developed high ridge near the Ural mountains and Okhotsk Sea and the stronger trough around Lake Baikal have offered a favorable circulation background for the EP in Lake Poyang area in June, 1998. Because of the strengthened Western Pacific subtropical high(WPSH), the stronger southwesterly in the northwest part of WPSH transported plentifiil moisture to the area, and it converged with the northerly around the Yangtze River valley. Meanwhile, the South Asia high was reinforced at upper layers, which led to strong ascending motion in Lake Poyang area. While the eastward shifted WPSH and ihe meridional developed circulation over the middle and high latitude at 500hPa reduced the moisture transport in Lake Poyang anea significantly in June, 2001. Moreover, the weakened north cold air from the trough around Lake Baikal was difficult to reach Lake Poyang area, and the weakened South Asia high decreased the ascending motion in the area.