In order to treat the cut-and-fill embankment economically and effectively, geogrid was adopted to reinforce the filling body in cut-and-fill sections. After the discussion of causes of the pavement diseases and the mechanism of geogrid reinforcement, the triaxial geogrid was introduced with its special mechanical characters, and forces analysis of geogrid was carried out to establish a tension calculation model. Through the analysis, the theoretical calculation formula of geogrid tension was obtained, it could be used to calculate the tensile force of geogrid at the junction, which was also the required anchoring force for the geogrid at the anchorage point. Then, according to a typical embankment section in Chang-zhi to An-yang expressway, a finite element model was established to study the variation laws of tension of geogrid, lateral displacement and differential settlement of pavement. The results show that the triaxial geogrid reinforcement could reduce the differential settlement and lateral displacement of cut-and-fill embankment more economically and effectively than traditional geogrids.