A new solid-state NMR experimental equipment was developed to monitor the structural change of polymer and protein fibers under active uniaxial deformation. The equipment was applied to monitoring change in the structure of a biodegradable aliphatic polyester fiber, poly(tetramethylene succinate) (PTMS; [-O(CH2)(4)OCO-(CH2)(2)CO-](n)), as a function of tensile stress. The crystal transition from alpha to beta forms for PTMS was induced by stress and monitored by the change of the methylene region in the C-13 NMR spectra. The C-13 chemical shielding constant for the model compound of poly(tetramethylene succinate) was calculated using the GIAO-CHF (gauge in-variant atomic orbitals-coupled Hartree-Fock) with ab initio 6-311G** basis set. This calculation acceptably explains the experimental results.