The strength criterion of soil in plane strain state is set up according to the strength criteria of Mohr-Coulomb, Lade-Duncan, general Mises, Matsuoka-Nakai, AC-SMP, plane strain condition and associated flow rule. The analyses of strength criteria in different plane states are made to determine the variation laws of the ratio of major principal stresses to minor principal stresses with internal friction angle. The applicabilit of every strength criterion is also analyzed. When the friction angle is less than 30°, the differences among different criteria are insignificant; otherwise, the differences become significant gradually. When internal friction angle is large enough, general Mises strength criterion in plane strain is not applicable to describe the failure of soil. Considering the cohesion effect, the strength criterion of cohesionless soil in plane strain state can be applied to cohesive soil and every strength criterion is verified by the plane strain test of loess. The results show that the Matsuoka-Nakai strength criteria is suitable for describing the strength of sand soil , and Lade-Duncan, AC-SMP strength criteria can characterize the strength of loess.