The selective oxidation of styrene on oxygen-covered Ag(110) and Ag(111) surfaces is studied by density functional theory (DFT) calculations with the periodic slab model. On the Ag(110) surface, a pre-adsorbed oxygen atom prefers the 3-fold hol ow site (3h) with an adsorption energy of-3.59 eV. On the Ag(111) surface, the most stable adsorption site for a pre-adsorbed oxygen atom is the fcc site, and the adsorption energy is-3.69 eV. The reaction process of the selective oxidation of styrene includes two steps: the formation of surface intermediates (branched oxametal acycle and linear oxametal acycle) and the subsequent formation of different products. The calculated results show that the formation of styrene oxide via the linear oxametal acycle (i.e., the pre-adsorbed atomic oxygen bound to the methylene group in styrene) is the favorable reaction mechanism on both Ag(110) and Ag(111) surfaces. The reaction barriers for the different reaction steps of styrene epoxidation on the Ag(110) surface are general y higher than those on the Ag(111) surface. Moreover, the micro-kinetic simulation results indicate that the relative selectivity towards the formation of styrene oxide on the Ag(111) surface is much higher than that on the Ag(110) surface (0.38 vs 0.003) because the energy barrier for the styrene epoxidation is smal er than that for the formation of phenyl acetaldehyde and its combustion intermediate on Ag(111) surface. The reverse trends occurred on the Ag(110) surface.% 采用密度泛函理论(DFT)对苯乙烯在Ag(110)表面和Ag(111)表面的环氧化反应进行了计算研究.经计算，在Ag(110)表面预吸附氧原子更易吸附在3重穴位(3h)，吸附能为-3.59 eV；在Ag(111)表面预吸附氧原子的最稳定吸附位是fcc位，吸附能为-3.69 eV.苯乙烯的环氧化反应过程首先经过一个金属中间体，然后再进一步反应变为产物，其中经过直链中间体较支链中间体更加有利. Ag(110)面的反应活化能一般大于Ag(111)面的，并且微观动力学模拟结果表明， Ag(111)表面生成环氧苯乙烷的选择性要明显高于Ag(110)表面(0.38与0.003)，原因是Ag(111)面环氧化反应活化能小于苯乙醛及燃烧中间体的活化能，而在Ag(110)上正相反.
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