The utility model provides an ultra high pressure cylinder for ten thousand tonner large structure accuracies are weighed, includes: one go up the saddle, with last saddle pass through spherical surface contact lower saddle, install the hydro -cylinder below saddle down the cylinder body, install the flexible displacement sensor in saddle and cylinder body down, wherein, the internally mounted ofcylinder body has the piston rod, central piston rod is equipped with to inside the overlapping of piston rod, central piston rod passes through the jacking of hydraulic oil promotion piston rod, displacement signal is then export magnetostrictive displacement sensor to through the four -core aviation socket who is located the hydro -cylinder neck, install lock nut and retaining ring on the hydro-cylinder, after the jacking structure thing was accomplished to the hydro -cylinder, lock nut and retaining ring be two effects together, made the hydro -cylinder realize mechanical auto -lock. The utility model discloses not only can weigh to ten thousand tonner large structure, and, can also be under hydraulic cylinder's emergency, realize the mechanical self -locking function of two effects, the large structure's that has ensured to be weighed safety.