Salinity may affect the intensity of onion (Allium cepa L.) because onion is classified as a salt-sensitive crop. To better understand these flavor changes, two experiments were conducted to evaluate changes of flavor components in Granex 33 onion in a salinity environment. The first experiment reported that S-alk(en)yl cysteine sulfoxides (ACSOs) change in response to salinity levels. Methyl cysteine sulfoxide (MCSO) increased as a percentage of total ACSOs and the ratio of 1-propenyl cysteine sulfoxide (1-PRENCSO) to total ACSOs decreased as NaCl increased. To speculate on the result of first experiment, we thought that sequential addition of NaCl would affect onion flavor intensity. A second experiment was conducted to investigate whether onion flavor quality changes were associated with sequential addition of NaCl. Results indicated that during the active bulbing stage, onion started to accumulate ACSOs. It is thought that active bulbing would be a key metabolic step for biosynthesis of onion flavor.