The selection of vacuum bellows must be based on the comprehensive constraints of displacement compensation, pressure bearing, fatigue life, and vacuum compatibility under system operating conditions. The primary parameters are effective area and stiffness coefficient: effective area determines the axial force response characteristics, while stiffness coefficient affects the dynamic stability of the system. The two are precisely controlled through the combination of wave height, wave distance, number of layers, and wall thickness. The displacement capacity is determined by the maximum allowable compression/tension of a single-layer ripple and the total wave number. In typical designs, the axial displacement limit of a single wave is taken as 0.3-0.4 times the wave height. Exceeding the limit will result in local buckling of the valley or plastic deformation of the peak. The pressure bearing capacity needs to be checked for the circumferential stress and axial instability critical load of the corrugated pipe under internal pressure, and the interlayer stress superposition calculation of the austenitic stainless steel multi-layer structure must be carried out according to the EJMA standard. The material selection must match the working medium and temperature range. 316L is suitable for chlorine containing environments, while Inconel 718 is used for high temperature conditions above 250 ℃; Surface treatment requires electrolytic polishing, Ra≤0.2 μm， And detected by helium mass spectrometry, with a leakage rate of ≤ 1 × 10 ⁻¹¹ Pa · m ³/s. The end connection form directly affects the assembly accuracy and sealing reliability: the straight welding end requires a concentricity deviation of ≤ 0.05 mm for the connecting pipe, and the flange welding end must ensure a flange surface perpendicularity of ≤ 0.02 mm/m. Fatigue life prediction requires inputting the actual cyclic load spectrum and calculating the equivalent effect amplitude according to the Nelson model to ensure that the design life is not less than 10 ⁵ full stroke cycles. The installation eccentricity, lateral misalignment, and torsional stress must be controlled within the allowable angular deviation of ± 0.2 °, otherwise it will significantly reduce the actual service life.