In quantum field theories, analyticity of scattering amplitude is a very important property. It is derived from general postulates of relativistic field theories. In a nonrelativistic potential model with a compactified spatial coordinate, it was shown some time ago that the scattering amplitude does not satisfy dispersion relations for a class of potentials under certain circumstances. Whereas for such models without a compact coordinate dispersion relations have been derived in the past. The perturbative Green function technique was adopted in the work concerned. We examine analyticity of scattering amplitude, in the LSZ formulation, for a field theory with a compact spatial dimension and discuss the consequences.