The effect of inhibition on N-nitrosodimethylamine (NDMA) formation by methanol extracts from 6 kinds of citrus seed (Citrus sunki, Citrus natsudaidai, Citrus suleata, Citrus tangerina, Citrus grandis and Citrus obovoidea) were investigated. The contents of moisture, crude protein, crude fat, carbohydrate, ash, flavonoid and totat phenol in citrus seeds were 4～6, l1～15, 32～46, 22～45, 2～4%, 12～24mg% and 53～133㎎%, respectively. The solid contents and yield of citrus seed extracts were 0.8～1.0 and 0.7～1.1%, respectively. Nitrite-scavenging activity by methanol extracts from citrus seeds increased with increasing extract dosage. Furthermore, the nitrite scavenging activity was pH dependent being the highest at pH 1.2 (42.7～96.9%) and the lowest at pH 6.0 (19.9～62.6%). Scavenging effects of nitrite by reaction time showed high effects under 3hr reaction time. The inhibition effect of NDMA formation by the citrus seed was strengthened as the amount of extract increased. The inhibition rate of methanol extracts from citrus seeds on NDMA formation showed 1.2～39.8%, 21.3～60.1% and 47.4～94.0%, according to add 1, 3 and 5㎖, respectively. Therefore, the inhibition effect of NDMA formation by the citrus seed was strengthened as the concentration of extract increased.