The outstanding climbing skills on smooth solid surface of some insects like beetle, bee and cockroach or some small reptiles like gecko have been under investigation for a long time. When some kinds of insects crawl on a smooth glass surface, the micro_pads leave traces of self-secreted organic liquid, which suggests that, the thin layer of confined liquid may contribute to the bioadhesive force between the micro_pad and the smooth surface. To investigate the properties of the confined liquid thin film, a series of experiments were carried out on a home-made microtribometer with a trace amount of ionic liquid (［emim］ ［Tf2N］) or PAO(poly_α_olefin) oil confined between a nano-scale smooth steel sphere and a glass plate. For a critical confined volume of pitoliters to nanoliters, and a critical clearance of tens to hundreds of nanometers, confinement-induced spontaneous spreading and abrupt shrinking were observed, accompanied by the presence of a stable interfacial adhesive force of remarkable magnitude. This spreading/shrinking-induced adhesive force was proved to be fundamentally different from the common meniscus capillary force and was considered to stem from confinement-induced solidification, according to our further investigations. The confinement-induced adhesive force of organic liquid may shed significant light on the physical principle “employed” by insects to crawl quickly on smooth vertical surfaces. By subtly adjusting the volume of confined liquid or the clearance between the pads and the surface, insects can control (i.e., switch on or off) the interfacial force at will. The interfacial bonding force of confined liquid thin film discovered in this paper may provide a basis for the principle of biomimetic attachment systems.