Extreme hydrological events occur with increasing frequency and the spatial and temporal distributions change significant-ly under the inhuence of constant change of the global climate. One of the hot issues in the field of hydrology and water resourcesis the uncertainty of threshold and its spatial and temporal distribution of extreme hydrological events.Based on daily precipitationdata of the 62 rainfall stations in the Pearl River Basin from 1959 to 2009,a study on the spatial and temporal distribution anduncertainty of the threshold of extreme precipitation was made systematically based on fixed critical value method, special percentilevalue method and goodness of extreme value distrbution fitting test. This study shows that studying the precise meaning of thethreshold of extreme precipitation at the basin-scale by the mentioned methods leads to some uncertain problems.The effects of theunbalance of spatial and temporal distribution on the threshold of extreme precipitation can't be reflected by fixed critical valuemethod. Using special percentile value method, the thresholds of extreme precipitation of the same percentile value under differentregions or of different percentile values in the same area are significantly diverse，because of the shortage of the standard. The ac-curacy of the threshold of extreme precipitation calculated by the goodness of extreme value distribution fitig test is limited, forthe uncertainty of extreme value distribution and the error of data of extreme value.