The intercalation reaction of polyoxyethylene sulfate (PEGS) with Mg-Al-nitrate [Mg-Al-NO3] layered double hydroxide (LDH) was investigated by using X-ray diffraction, infrared spectroscopy, and transmission electron microscopy (TEM). X-ray diffractograms showed that the basal spacing of the [Mg-Al-NO3] LDH with PEGS as the intergallery anion expanded from 0.89 to 2.37 nm to form [Mg-Al-(PEGS)], but no expansion of the basal spacing was observed when poly(ethylene glycol) (PEG) reacted with [Mg-Al-NO3]. The characteristic absorption bands of the organic anion in the infrared spectra were obtained after prolonged treatment with deionized water, demonstrating the stability of the intercalation compounds. Furthermore, TEM analysis revealed that [Mg-Al-NO3], which consisted of hexagonal particles approximately 100-120 nm in length, changed into monodisperse rigid spheres approximately 200 nm in diameter after the intercalation of PEGS.