Layered double hydroxide(LDH) was synthesized from the mixture of magnesium hydroxide and aluminum hydroxide with microwave irradiation. It has been compared with that of conventional heating method in the respect of crystallization time, structure, morphology, particle size, and its anion exchange capacity. The microwave speeded up the crystallization rate of Mg-Al-LDH so that the XRD patterns of LDH was observed from the sample after microwave hydrothermal treatment, while the crystal phase was hardly observed from that prepared by conventional hydrothermal method before drying process. Mg-Al-LDH prepared with microwave irradiation seemed to have slightly higher Mg/Al molar ratio even with the same compositions of starting materials and the lower anion exchange capacity after 1 day exposure in 0.1 N NaCl solution compared to the conventionally prepared one.