We perform the first-principles study of the structural properties and the high temperature phase stabilization of Cr, W-doped β-La2Mo2O9. We find that Cr prefers the site with four coordination numbers and W atom preferentially occupies the site with five coordination numbers. The nonlinear dependence of cell parameter on W content in W-doped systems results from the nonlinear change in Mo(W)-O and La-O bond lengths with W content and the decrease of coordination number around W occupied site. The decrease of cohesive energy with the W-doped concentration is conducive to the understanding of the stabilization of the β-La2Mo2-xWxO9 at lower temperature. The appearance of stronger W-O bond leads to the increase of the energy barrier of oxygen-ion concerted motion in W-dopedβ-La2Mo2O9.