The polarizer is an indispensable optical element to liquid crystal display (LCD). PVA-iodine polarizer is utilized to various LCD widely for the excellent optical property. The PVA-iodine polarizer is prepared by stretching and dyeing PVA with iodine. The characteristic of PVA-iodine polarizer is controlled by quantity and orientation of two complexes of I3- and I5-. The technologies and the technical trends of polarizer for LCD are introduced.