Abstract: For the natural soft ground with plane strain under the self-weight of embankment filling, analytical formulae for both the critical load of soft ground and the critical filling height of embankment are proposed based on the generalized spatially mobilized plane (SMP) criterion with reasonable consideration of the intermediate principal stress. The lateral pressure coefficient and consolidation degree of soft ground are also taken into account, and more applicable conditions of the obtained analytical formulae are provided. Finally, the parametric studies combined with the results of Mohr-Coulomb (M-C) criterion are discussed. By comparing with the results of the existing literatures, these analytical formulae are validated, and the necessity of given applicable conditions is highlighted. It is found that all the effects of consolidation degree, lateral pressure coefficient, cohesion and inner friction angle on the critical filling height of embankment are very significant and the consolidation degree should not be blindly adopted as 0 or 100%. The results of M-C criterion are conservative, whereas the minimum lateral pressure coefficient of the proposed formulae is smaller due to the effect of the intermediate principal stress, and thus its application range is wider. The real lateral pressure coefficient of soft ground should be determined by in-situ tests, and the variability of its strength parameters should be fully considered.