The chemical composition of essential oil (1.18% yield) from celery seeds by hydrodistillation extraction method was analyzed by GC-MS. A total of 23 constituents were detected, in which 18 compounds that account for 91.38% were identified. The main constituents were limonene (31.15%), β-selinene (22.28%) , p-cresyl isovalerate (14.94%), α-2-propenylbenzenemethanol (9.872% ), β-myrcene (4.32%) and α-selinene (4.32%). The abilities of scavenging DPPH radical of the essential oil and hydrodistillation residue were studied. The result indicated that the maximum scavenging rates was 98.1% when 0.20 mL of the oil was used. The extracts of residue by methanol, ethanol and acetone also has remarkable scavenging activity. The result showed that the scavenging rates of the methanol, ethanol and acetone extracts of the residue were 91.5%, 91.2% and 56.2% respectively, when 0.10 mL of the extract solutions was used.