Buckling and springback defects are easily to be produced on the thin-walled aluminum alloy tubular components when they are manufactured by the hydro-pressing process. In this paper, the cross-sectional buckling and springback behavior of the thin-walled 5A06 aluminum alloy tube blanks with D/t greater than 50 during the hydro-pressing process using a die with middle parting structure were researched by the experiment and numerical simulation. The effect of the internal pressure loading path on the cross-sectional shape and size of the tubular components was firstly discussed. Then, the buckling and springback mechanisms of the cross-section were revealed during the hydro-pressing process. It is shown that the cross-sectional dimension deviation of the tubular components obtained under a constant internal pressure of 0.15ps or a stepwise increasing internal pressure from 0 to 1.00ps with the upper die movement is lower than that under the constant internal pressures of 0.25ps and 0.50ps. During the hydro-pressing forming process, a large bending deformation that occurs on the edge of the unsupported area will lead to buckling defect. Moreover, the deformation behavior of the straight wall is affected by the bending moment in the corner during the unloading process. On the one hand, a concave deformation happens on the straight wall during the unloading process of internal pressure. On the other hand, the concave cross-section will spring back outward in the process of die opening.