Partial saponification of polyvinyl acetate with sodium hydroxide or potassium hydroxide was carried out in acetone-water (7/3, V/V) mixture, and the effect of the above two alkalies were compared. In order to investigate the sizing effect of sodium alginate for the use of synthetic fibers, the amount of size, elongation and strength of sized yarn were examined. It was found that the treated nylon and polyester filament yarns prepared from polyvinyl alcohol and Na-alginate had better qualities as anti-static agent.