Abstract: The mechanism of blast densfficalion of saturated sand has been discussed by observing and analyzing the phenomena and result of model experiments. It is pointed out that specilic charge’s weight is not the main physical parameter in blasting densification of saturated sand, and an empirical formula is giten between surface setilement and blast effective range. The result shows that disruption and rearrngement of sand caused by blasting vibration are the major reason for sand densification.