Abstract: Through the first principle calculation based on density functional theory (DFT), the cesium adsorption behavior on tungsten (110) surface was investigated. The calculation results show the maximum cesium adsorption rate defined by relative atom number of a monolayer is 0.4, and the cesium adsorption location alters with the increase of adsorption rate according to the adsorption energy calculation. The long bridge location is the most likely adsorption position for cesium atom at the adsorption rate of 0.25. A new surface adsorption periodic structure of-ABA′B′-style appears and the adsorbate forms a complete monolayer when the adsorption rate is 0.4. As the cesium adsorption rate increases, the work function decreases at first and then increases until reaching a plateau of 2.134 eV. The work function minimum value of 1.524 eV appears at the adsorption rate of 0.25, lower than work function of pure cesium (110) surface. The calculation results of the dipole model and partial density of state (PDOS) show that the mechanism of electron transfer from cesium atom to tungsten surface and the change of electron energy distribution contribute to the decrease of surface work function.