<p>Assuming that the soil arch is an authentic spatial soil arch of semi-ellipsoidal shell, a new method for predicting limit pile efficacy of pile-supported embankment was proposed considering spatial soil arching effect and nonuniform distribution of vertical stress on subsoils between piles. Analyzing the static equilibrium of the crown of the spatial soil arch yielded the pile efficacy for the plastic point at arch crown, considering surcharge and nonuniform distribution of the vertical stress on subsoils. And analyzing the static equilibrium of the foot of this spatial soil arch gave the pile efficacy for the plastic point at arch foot (i.e. pile top or cap). Further, the effects of parameters on the pile efficacy were discussed as well as whether the plastic point of spatial soil arch appears at the arch crown or at the pile top. Moreover, the comparisons of the pile efficacy shown that the proposed method is safer and more reliable than the existing methods to predict pile efficacy of pile-supported embankment.</p>