At present

the method for determining anchorage angle of foundation beam with prestressed anchor-cable is usually the same as that in the prestressed anchorages engineering. Therefore

some slopes cannot be reinforced efficiently by foundation beam with prestressed cable because of the unreasonable designed anchorage-angle. A new method for designing the reasonable anchorage-angle is proposed. Firstly

an initial criterion there is no slip between the beam and the slope surface is proposed. Secondly

the highest possible anchorage power must be obtained in the design

and it is the design objective. Prestressed utilization-ratio is defined as the ratio of the real anchorage stress to anchor-cable prestress. So

the anchorage angle can be determined rationally considering the initial criterion and the utilization-ratio and giving attention to the economic and construction factors. Finally

an engineering example is given to explain how to use this method in practice.