In a field experiment, the effect of sulphur was studied on mustard variety Varuna at student's Instructional Farm of N.D. University of Agriculture & Technology, Kumarganj, Faizabad. Four levels of sulphur were applied viz., S0 (Sulphur@ 0 kg ha-1) S1 (Sulphur @ 20 kg ha-1), S2 (Sulphur @ 40 kg ha-1) and S3 (Sulphur @ 60 kg ha-1) in the form of gypsum which has 18.9 per cent available sulphur. Normal recommended doses of other fertilizers were also applied. Sulphur significantly influence the vegetative growth, yield and also significantly improve the mustard oil quality. Oil content ranged from 38.14-40.15 percent, iodine value 100.4-101.32 and acid value 13.28-13.45. Application of sulphur significantly reduce the saponification value from 171.86-158.29. In the mustard cake the total mineral content was also significantly increased 3.98-4.19 per cent and essential amino acids, Tryptophan (g.57-1.08 g/16 g N), Lysine (3.57-3.99 g/16 g N) and Methionine (0.88-1.26 g/16 g N) content also. Sulphur significantly increases the poly unsaturated fatty acid content like linoleic acid (14.33-14.43%), linolenic (13.64-14.10%) palmitic acid (3.11-3.45%) stearic acid (0.17-0.20%) and oleic acid (13.28-13.38%). It significantly reduce undesirable fatty acid content like eicosenioc acid content (6.34-6.01%) and eruic acid from (48.29-48.17%) and thus improve the oil quality.