Abstract: The study aims to analyze the effect of drought treatment on the growth and accumulation of flavonoids in celery. The change of biomass, osmolyte, antioxidant enzyme system, key enzyme in flavonoids metabolize and flavonoid accumulation in celery variety‘Shenqin 1’are studied by solution culture under mild drought (10% PEG6000 treatment) and severe drought (30% PEG6000 treatment). In mild drought condition, compared with control, no significant difference in biomass and H2O2, O2ˉ·content was observed; proline and soluble sugar content, antioxidant enzyme activity, phenylalanine ammonia lyase (PAL), chalcone synthase (CHS) and chalcone isomerase (CHI) activity and apigenin and luteolin content increased significantly. Compared with those of control, the apigenin content in leaf blade and leaf stalk was increased by 36.05% and 40.35%, respectively, and luteolin content was increased by 34.39% and 43.09%, respectively. Under severe drought condition, compared with control, the biomass of celery was significantly decreased, the plant height, shoot dry weight and root dry weight reduced by 34.47% , 36.02% , 59.09% , respectively. Compared with control, no significant difference in proline and soluble sugar content was observed, H2O2, O2ˉ·content and antioxidant enzyme activity increased remarkably (CAT activity was significantly lower than mild drought treatment); there was no significant increase in apigenin and luteolin content, and CHS and CHI activity were significantly reduced compared with that under mild drought stress. The change of the indexes mentioned above was almost the same in leaf blade and leaf stalk. It is concluded that mild drought (10% PEG6000 treatment) could keep a normal growth and meanwhile promote the accumulation of flavonoids in celery.