Abstract: The dry seeds of oil sunflower were irradiated with the carbon ion beam provided by the Heavy Ion Research Facility(HIRFL) in Lanzhou. To research the effects of carbon ion beam irradiation on the fruiting characters of M1 oil-sunflower, the seedling emergence rate, survival rate, pollen viability, stigma receptivity and seed setting rate under different pollination conditions were measured. The results showed that the seedling emergence rate, survival rate, pollen viability and seed setting rate reduced with the irradiation dose increasing. Compared with control, the emergence rate and survival rate of oil-sunflower decreased by 55.68% and 64.66% after seeds irradiated with a carbon ion dose of 80 Gy. This study also revealed that seeds were irradiated with 20~160 Gy showed very low self-cross seed setting rate, and the mixed-cross seed setting rate were significantly reduced at irradiation of 40~160 Gy. Pollen viability decreased from 92.01% of the CK to 47.59% of the 160 Gy irradiation. With the irradiation dose increasing, the percentage of stigmas with higher receptivity reduced, and the percentage of stigmas with lower receptivity and no receptivity increased. All results indicated that the damage of carbon ion beam irradiation inhibited the fertility of flower organs and reduced the seeding rate. According to the semi-lethal dose of survival rate and the semi-sterile dose of mixed-cross seed setting rate, the recommended irradiation dose range of oil sunflower is 55 to 153 Gy. Our findings may lead to more reference for the selection of suitable irradiation dose for oil sunflower breeding by carbon ion beam irradiation.