Multiple-cable single borehole anchorages are widely used in China, accepted and regarded as a very effective method for slope protection, landslide remediation and foundation ditch support. This paper presents a new method for testing tensional stresses of individual steel strands within anchor cables in single boreholes. A rig has been designed to permit testing of cables within a single borehole, including two special features: a metal plate that distributes tension between strands of a cable and a sensing device that measures the stress in each individual strand. The feasibility of the method has been demonstrated by an in situ tensional stress test on anchor cables at a landslide remediation site that successfully measured the forces on individual steel strands fastened to different anchorage segments within a borehole. The steel cable strands displayed nonlinear extension characteristics; and the length of anchorage segments and grout strength met design criteria. The results confirm that this design of anchorage is satisfactory and can provide valuable data for future design and construction.