IBSS_Gecko_6 is a bio-inspired legged robot that can climb on smooth vertical surface. In this paper, we design a new footpad which equipped with polyurethane adhesive. Different from pervious study, we directly apply the adhesive in the footpad and investigate optimal attaching and detaching trajectory for wall climbing. The optimal adhesion force demonstrated that the leg can perform strong attaching force and modest detaching force, which can supply a reliable force for wall climbing. The optimal trajectory can apply in the wall climbing robot in future.