Abstract: In order to facilitate machinery harvesting, flax cultivar‘Jinya12’was used to investigate the effect of diquat on dehydration and seed quality of flax. When 80% of bolls turned to be brown, flax plants were treated with diquat, and water content, germination rate, thousand-seed weight, fatty acids of flax seeds were measured. The results showed that, compared with the control (natural mature after water spray), plants and seeds under diquat treatment were remarkably dehydrated after 6 days, the water content of plant and seed were 14.2% and 4.2% respectively, which were significantly declined by 48.36% and 39.13% respectively compared with that of the control. Diquat could significantly increase the contents of oil and linolenic acid, and significantly reduce the contents of oleic acid and stearic acid, although it had no significant effect on germination rate and thousand- seed weight. Therefore, it is proposed to promote diquat in herbicide registration as a ripener on flax.