Abstract: Zhouqu "8.8" extremely big debris flow caused severe damages and has been the world focus.Potential debris flows still exist after the "8.8" disaster.The first difficulty that the government faces during post-disaster reconstruction phase is the determination of the fortification standard of the reconstruction works.Based on the analysis of the temporal and spatial distribution characteristics of the rainfall which triggered the "8.8" Zhouqu extremely big debris flow,we found that the rainfall has characteristics such as being heavy,short duration and obvious local variations.Based on the above,it is suggested that the characteristics of the rainfall should be fully considered in the design of comprehensive treatment projects of debris flow during post-disaster reconstruction phase.That is to take the condition when the whole Sanyanyu is covered by the same rainfall magnitude of this time as the most unfavorable extreme circumstance to calculate the maximum flow.