Abstract: In order to find out the difference of nutrients and antioxidant activities among different species of Brassica oleracea L. var. and the influence of cooking on it,cauliflower,loose-curd cauliflower,broccoli and Romanesco cauliflower were collected to determine vitamin C,total carotene,total flavonoids,total phenol and antioxidant activities. The effects of cooking methods including boiling,steaming,microwaving and stir-frying on Brassica oleracea L. var. were also studied. The results showed that there were significant differences in nutrients and antioxidant activities among different species of Brassica oleracea L. var. Among them,the contents of vitamin C,total carotene and total flavonoids in Romanesco cauliflower were the highest with 75.67 mg/100 g,39.24 μg/100 g and 4.34 mg RE/100 g,respectively. The content of total phenols in broccoli was the highest with 38.04 mg GAE/100 g,and higher than cauliflower and loose-curd cauliflower in the contents of total carotene and total flavonoids. Except of total phenols,loose-curd cauliflower processed the higher contents of nutrients than cauliflower. The free radical scavenging capacities of DPPH and ABTS of broccoli were the highest with 68.40% and 28.00%,respectively,followed by Romanesco cauliflower. The FRAP reduction capacities of cauliflower and loose-curd cauliflower were higher and with no significant difference(P>0.05). Cooking had different effect on the nutrients and antioxidant activities of Brassica oleracea L. var. The content of vitamin C had different degrees of loss during cooking,while total carotene was both lost and improved. The contents of total flavonoids and total phenols were overall improved. DPPH and ABTS free radical scavenging ability had improved,while FRAP reducing ability was just the opposite. Steaming in different cooking methods had a better effect on the nutrients and antioxidant activity,followed by microwave,boiling and stir-frying. The nutrients and antioxidant activities of different species of Brassica oleracea L. var. obtained in this experiment can provide a basis for the consumption of Brassica oleracea L. var. and the choice of cooking methods for specific populations. It can also provide basic data for consumers to assess the risk of nutrients intake through diet.