In the framework of limit equilibrium analysis

stability of slope protected by soil nailing is analyzed by using a new method of searching for sliding surface and circular sliding surface method. When considering earthquake

pseudo static method is adopted. Then

according to different modes of slice

a formula of calculating dynamic distribution coefficient of horizontal seism is derived. Aiming at the shortage of vertical slice method of circular sliding surface under earthquake

the mode of combining horizontal slice method with vertical slice method is used. Through analyzing examples and studying the effect of space change of soil nailing and length of soil nailing under different earthquake intensities on the static and dynamic stabilities of slope protected by soil nailing

some conclusions are obtained. The minimum factor of safety (FOS) calculated by new method is quite close to that calculated by circular sliding surface method

and is also smaller than previous results

so it shows that the new method of searching for sliding surface is feasible. In analyzing the static and dynamic stabilities of slope protected by soil nailing

the critical sliding surfaces got by the new method is close to the those got by critical circular sliding surfaces

but they perform the characteristics of non-circular feature. Reducing space of soil nailing and increasing length of soil nailing to a certain degree can effectively improve stability of slope protected by soil nailing under earthquake.