Abstract: In view of the large number of plane strain problems in loess engineering, more studies have been carried out under the condition of isotropic consolidation, but it is not consistent with the actual stress state of the soil. The true tri-axial apparatus after plane strain modification is used to simulate the actual stress state of the soil. Through the initial loading plane strain tests under different initial consolidation stress ratios, moisture content and confining pressure of the original loess, different initial consolidations are revealed. The influence of initial consolidation stress ratio, water content and confining pressure on the strength characteristics of intact loess is discussed and the change law of intermediate principal stresses during failure are summarized. The results show that the strength of intact loess under anisotropic consolidation increases with the increasing initial consolidation stress ratio, and is significantly greater than that of equalized consolidation. The strength of intact loess increases with the increasing initial consolidation stress ratio, and is significantly greater than the isotropic consolidation. The shear strength and the p and q at failure decrease with the initial consolidation stress ratio. The decrease of water content increases, and the degree of damage to the primary structure of the soil increases with the increasing initial consolidation stress ratio, which reduces the cohesion. When the secondary structure forms the compaction of soil particles, the internal friction angle increases. The intermediate principal stress at the time of failure increases with the increasing initial consolidation stress ratio. The intermediate principal stress coefficient at the time of failure ranges from 0.15 to 0.45. The effect of consolidation confining pressure and water content of the intact loess under the plane strain conditions on the intermediate principal stress coefficient is obvious. The research results will further improve the plane strain test research of intact loess, and can solve the problem of loess engineering construction under the plane strain conditions, and also provide test basis and theoretical basis.