The measured values of the longitudinal stress in the full size hydraulic track test model are different from the values calculated by the Chinese applicable codes. This problem is studied by use of the theoretical derivation, numerical calculation and FEM. Studies indicate that the particular boundary conditions and forces exerted on the hydraulic track are the main reason of the normal stress of cross-section in track being different from the general beam theory. The bending stress of bottom of the track appears a biggest-range descent due to horizontal resistance between track and concrete foundation. And the normal stress of cross-section in the top of the track occurs a wide-range ascent due to the superimposed effect of local load of wheel-track contact and bending moment. The formulas proposed in this article can be used for structures design. This analysis can well explain the phenomenon occurring in the test of bending stress of track which is the supporting structure of fixed-roller wheel high-pressure gate of TGP.