The invention discloses an end assembled fixture of a true triaxial apparatus. The end assembled fixture of the true triaxial apparatus comprises a transitional steel tank, wherein the transitional steel tank comprises a rectangular bottom plate and three rectangular side plates arranged along the lateral side of the bottom plate, and all of the bottom plate and the side plates are steel plates and connected into a whole; rubber pads which are attached to the side plates are arranged both on the inner side and the outer side of each of the three rectangular side plates, hexagon socket bolts penetrate through the external the rubber pads to be connected with the side plates through screw threads, and pressing forces of the hexagon socket bolts for the internal rubber pads are used for fixing the inner sides of the three side plates and an original moving head of the true triaxial apparatus; the bottom plate and a confining pressure loading plate on the outer side of the bottom plate are fixed through hexagon socket fastening bolts on the inner side of the bottom plate; the size of a loading surface of the confining pressure loading plate is determined according to the size and the shape of a loading component. The end assembled fixture of the true triaxial apparatus can expand the size and shape limit values of the loading component for the true triaxial apparatus, and further can improve the service life and loading authenticity of the apparatus; and the end assembled fixture has a simple structure, and is convenient to assemble, safe and reliable in operation, and good in economic engineering utility.