A composite retaining structure composed of reinforced soil retaining wall and anti-slide piles is proposed to solve the construction problems in high fill embankment upon soft soil. Finite difference software FLAC^3D was used to establish the numerical models of composite retaining structure. The influences of cast mode of panels on lateral displacement of wall surface,lateral earth pressure behind retaining walls,lateral displacement and bending moments of anti-slide piles and stress distribution of geosynthetic geogrids were analyzed. Numerical results revealed a linear distribution of lateral displacement of panels in post-cast rigid mode and the maximum displacement at the top of walls. Earth pressure on post-cast panels was far less than that on rigid panels. Moreover,the displacement and bending moments of anti-slide piles in the composite retaining structure with post-cast rigid panels were larger than those in the structure with rigid panels. The largest tensile stress of geosynthetic geogrids in the structure with rigid panels was found at the junction between panels and geogrids;while for the structure with post-cast rigid panels,the position of the largest tensile stress deviated from the retaining wall as the layer of geogrids were higher.Composite retaining structure with post-cast rigid panel could be used and promoted in high embankment area on soft soil due to its good performance with small displacement and earth pressure on post-cast panel.