Abstract: Medium principal stresses have a significant effect on the stress-strain behavior of soil. To describe the stress-strain behavior of soil more accurately, it is necessary to carry out true triaxial tests in the field of soil mechanics. This paper introduces a new three-way rigid loading true triaxial apparatus independently developed by Xi'an University of Technology, including the pressure chamber composed of four bottom rolling and side sliding rigid plates, rigid specimen cap and rigid bottom plate, three-way servo-hydraulic stepping motor loading control system, computer and storage intelligent control system, and four parts of the water - air suction control system panel. By dividing the rectangular soil samples into true triaxial rectangular shear layer specimens and vertical principal stresses acting on the end of the transfer layer soil block, by the end of the transfer layer acting on the rectangular shear layer to transfer the vertical principal stresses with the side sliding rigid plate applying the role of orthogonal bi-directional principal stresses, to solve the technical problems of the traditional three-way rigid plate loading interferes with each other. Through the verification test of remolded loess and saturated sand, the rationality of the instrument is verified, and the failure mode of the sample and the cause of the test error are summarized. The apparatus has the advantages of simple operation, uniform deformation and automatic loading intelligent control.