In this paper, the occurrence of recoil and surface warp during flat surface-straight edge hemming process is investigated. A general-purpose finite element code ABAQUS/Standard is used to simulate the hemming operations. Reverse bending, localized buckling and springback are the fundamental mechanisms that cause surface warp and recoil. Recoil and warp are not independent. One parameter called final equivalent residual warp is obtained to represent both. Feasible pre-hem ending zone is proposed based on final equivalent residual warp. The influence of the geometrical and process parameters on recoil and warp are also investigated.