This paper investigated the network system self-assembled by β-cyclodextrin, surfactant and xanthan gum, based on the theory of supramolecular self-assembly, and analyzed the microstructure of the self-assembly system by Transmission Electron Microscopy(TEM), and evaluated the tolerance to temperature, salinity, calcium and its rheological properties. The network system greatly improved shear thinning and resistance to temperature, salt and calcium of xanthan gum. The microstructure difference between xanthan gum and the self-assembled system was evident, and the self-assembly system had obvious reticular conformation. The shear thinning and rheological properties of self-assembly system were superior to xanthan gum alone at low shear rates. The self-assembly system can tolerate saturated sodium chloride(26.5%), 4%CaC12 in 90 ˚C and resist high temperature(150 ˚C at least). Clay-free water-based drilling fluid with the self-assembly system had excellent rheological properties. The drilling fluid system with density of 1.6 g/cm3 aged at 150 ˚C had excellent filtration, and the filtration loss at High Temperature and High Pressure(HTHP) was 10.2 mL. All of the results suggested that supramolecular self-assembly greatly improved tolerance to temperature, salt, calcium and improved the shear thinning properties of xanthan gum, and promoted the application of clay-free water based drilling fluid in oil fields.