Bellows are special structures that require high strength as well as good flexibility. The design, manufacture, and analysis of bellow tubes thus are more complicated. Test of bellows to understand their mechanical behavior, and to verify a design purpose finite element program is needed for practical use. In this paper, digital-image-correlation method is applied to measure the stiffness of single- and double-ply bellows under axial compressive load and various internal pressures. The influence of the internal pressure on the stiffness of the bellows is investigated. The meridian and hoop strains at the crest of the bellows are measured by strain gages. The results show that tensile meridian and hoop strains on the single-ply bellows are found as expected. However, the compressive meridian strain is found on the double-ply bellows.