The invention relates to a widened embankment structure with a beside-water cliff high retaining wall fill section. The widened embankment structure is mainly composed of an original pavement structure, a transverse connecting reinforcement cage, grouted stiffeners, a new widened part pavement structure, a diagonal brace, a mortar rubble slope, a reinforced concrete continuous slab and a pre-stressed pipe pile, wherein the reinforced concrete continuous slab and the diagonal brace are arranged on the top of the pre-stressed pipe pile; one end of the diagonal brace is connected with the top of the pre-stressed pipe pile, while the other end of the diagonal brace is connected with a panel of an existing cantilever retaining wall; the grouted stiffeners are arranged on the base plate of the existing cantilever retaining wall and the bottom of the reinforced concrete continuous slab; the transverse connecting reinforcement cage is arranged between the panel of the existing cantilever retaining wall and an new widened embankment; a waterproof layer is paved on the upper parts of the reinforced concrete continuous slab and the grouted stiffeners, and a light embankment and the new widened part pavement structure are orderly cast on the waterproof layer; a slope protecting waterproof layer and the mortar rubble slope are arranged outside the slope of the new widened part pavement structure. The widened embankment structure with the beside-water cliff high retaining wall fill section is used for effectively solving the problem that the widening construction cannot be implemented as the existing cantilever retaining wall cannot be removed.