Abstract: Two crystal forms (α and δ′ form) of nylon 11 were prepared by melting, icewater bath quenching and annealing. The characteristic of chain movement of two forms was investigated using dielectric relaxation spectroscopy in the frequency range from 42 Hz to 5 MHz. The dielectric temperature spectra at different frequencies show that the primary αrelaxation corresponding to the chain segment movement is located at higher temperature in α form, indicating the chain segment movement is restricted after δ′→α crystal transition. The activation energy of secondary βrelaxation remained almost unchanged for two forms, but the relaxation time was longer and the relaxation strength was weaker for α form, confirming that the local relaxation was also restricted to some extent after δ′→α crystal transition.