Statistic methods of analyzing the correlation of historical landslides and rainfall data were always used to study the rainfall thresholds to trigger landslides, but those statistical analyses seldom thought about the rainfall infiltration mode which can affect the thresholds very much. In fact, different rainfall infiltration will trigger different landslide types and magnitudes, and different landslide types also "need" different thresholds to be triggered. This paper took the loess landslides as the studying objectives, analyzed and discussed the rainfall infiltration mechanisms in loess slope, preliminary established three triggering modes which are slow infiltration triggering mode, infiltration blocked triggering mode and integrated—infiltration passage triggering mode. It collected 227 landslides cases which having certain date records and occurred in 1960~2008, divided these cases into three groups according to the modes; used different statistical methods to analyze the correlations between landslides and rainfall, and established the rain thresholds or warning values for each infiltration and triggering modes.