Peel stress causing by secondary bending in composite-metal adhesively single lap joints will decrease strength of the joints. In this article it analyzes the effect of different ply orientation angle, different ply stacking sequence and chamfering to secondary bending of bonded single lap joints with finite element method. It also analyzes the relation between secondary bending and peel stress, bending stiffness. It discovers that the bending stiffness affects the peel stress; the bigger bending stiffness is, the smaller secondary bending is; the chamfering helps to reduce secondary bending.