In order to study the effect of different resistant sunflower root exudates on the germination of Orobanche cumana Wallr.,we collected the root exudates of three sunflower varieties by hydroponics and extracted with CH₂Cl₂.The dichloromethane extracts were then separated with silica gel column.The result showed that:(1)In a certain range of concentration,low concentration of sunflower root exudates promoted O.cumana seeds to germination,but high concentration inhibited it.(2)The germination rate was the highest when treated with 0.1 mg/mL dichloromethane extracts,O.cumana seeds germination rate under the ‘Xinghuodabaibian’ and ‘Baikuiza NO.9’ root exudates were 46.92% and 43.88%,immune variety ‘MGS’ was lower than the formers,germination rate was 27.81%.(3)The hexane-ethyl acetate(1∶1) fractions had the higher germination activity than other four fractions,O.cumana seeds germination rate under this fraction of ‘Xinghuodabaibian’,‘Baikuiza NO.9’ and ‘MGS’ were 49.90%,45.66% and 30.00%,respectively.(4)When added GR24 or dehydrocostus lactone to the root exudates of ‘MGS’,O.cumana seeds germination rate was decreased compare to GR24 or dehydrocostus lactone only,this indicated that the immune sunflower variety ‘MGS’ root exudates had the negative effect on the germination of O.cumana seed and there were some chemicals in its root exudates that inhibited the O.cumana seeds germination.