The study on characteristics of optical gas sensing materials after gas adsorption is a hot issue. The microscopic mechanism and optical characteristics of rutile titanium dioxide (110) surface adsorption NH3 molecules are studied. The results show that NH3 molecules are easy to be adsorbed by rutile titanium dioxide (110) surface containing oxygen vacancies. The higher of oxygen vacancy concentration, the more stability of NH3 adsorption, and the main way of surface adsorption NH3 molecule is negative charge center down. When oxygen vacancy concentration reached 33%, adsorption energy is 1.7313 eV. The adsorption of NH3 is chemical adsorption, and the H atom of NH3 is reduced and N atom is oxidized. In visible light range from 1.5 eV to 3.1 eV, the higher concentration of oxygen vacancy, the more obvious improvement of absorption, reflection ability and optical gas sensing performance.