The amount of excavation works on the rock slope of the Xindongmen Wharf Yard is large，and the excavation slope rate will have a greater impact on the project cost. In response to this problem，new slope ratio calculation formulas are explored based on the existing standard slope ratio. Compared with single lithologic quality classification （qualitative，RMR and BQ quantitative） and slope ratio method （classified value and fracture angle），the methods are innovatively proposed，such as the value of the shear strength gradient of a single lithology，the equivalent BQ quality classification of interbedded rock mass，and weighted thickness shear strength slope ratio method. And the on-site verification effect is better. It is concluded that：1）The slope ratio calculated by the formula method of shear strength slope ratio can make good use of rock mass self-stability，control slope safety，and optimize engineering quantity. 2）This method can provide a new idea for the quality classification and slope rate selection of similar interbedded rock mass slopes in the case of no weak outwardly inclined structural planes，insufficient groundwater，and non-stratified conditions.