The stability and catalytic activity of Au10,Au13 and Au20 clusters in water gas shift reaction(WGSR) were investigated by density functional theory(DFT); the adsorption behavior of reaction species and the reaction mechanism of WGSR on various Aun clusters were explored. The results indicated that the stability of three Aun clusters follows the order Au10 < Au13 < Au20,whereas their electron delocalization and adsorption capacity decreases in the sequence of Au13 > Au10 > Au20. Three Aun clusters exhibit t...