The chemical constituents of the fatty oil from seeds of Descurainia sophia(L.) Webb ex Prantl were analyzed by GC-MS. The results showed that thirty-four compounds were isolated and identified, representing 97.259% of the total fatty oil. The main constituents of oil were unsaturated fatty acids(31.745%), unsaturated fatty acid esters(38.631%) and saturated fatty acid esters(12.285%).The main compounds with contents over 10%(V/V) followed as: 9,12,15-calendic acid-2,3-dihydroxypropyl ester(14.763%),(9Z,12Z,15Z)-calendic acid ethyl ester(14.723%) and(Z,Z)-9,12-octadecadienoic acid(13.073%).