The calculation of sliding velocity of landslide is the basis of surge prediction. On basis of considering the resistance of water

the formulas advised by The American Society of Civil Engineers and movement equation method are improved. Taking the Xiatudiling landslide in the Three Gorges Reservoir of Zigui county for example

the average velocity and each slice’s acceleration

velocity in the process of sliding are calculated; the comparative analysis about the value and change law of acceleration

velocity is made between pre and post considering the water resistance; and then

the height of initial surge evoked by the landslide is calculated. It is concluded that considering the water resistance to slices entering water is more coincident to practical force condition. The water resistance has great influence on the acceleration

velocity of landslide. When the water resistance is not considered

with the increasing of numbers of slices entering water

the acceleration of landslide increases firstly

then it decreases

and the tendency will not rebound. When the water resistance is considered

the value of water resistance is related with velocity of landslide and area of slope surface; under the comprehensive effect of these two factors

the acceleration of landslide may increase after its decreasing tendency.