Abstract: Vicia unijuga is a valuable forage species in Gannan Tibetan region, and its seed production is important for planting and popularizing of V. unijuga in this region. Fruit-set patterns and selective abortion of flowers of V. unijuga in Gannan Tibetan region were studied. The results showed that: 1) In terms of time, the highest fruit set was observed for the two-year-old population (28.8%) at the full-bloom stage and for the five-year-old population (41.6%) at the early flowering stage. For both populations, the lowest fruit set (3.0% and 1.1%) was found at the end of flowering stage. There was no appreciable difference (P>0.05) in the seed number per pod between the early flowering and full-bloom stages for the two populations, and the seed number per pod at the end of flowering stage was zero; 2) On an inflorescence, the highest fruit set was in the middle of the inflorescence for both populations. The two-year-old population was 43.9% and the five-year-old population was 41.6%. However, the seed number per pod exhibited no significant difference (P>0.05) in each part of the inflorescence for the two populations; 3) The ovules closing to the stigma and pedicel were more likely to abort. The ovules in the 2^nd, 3^rd, 4^th and 5^th positions starting from the side of the stigma would have higher possibility to form mature seeds and showed alternating abortion patterns; 4) The number of fruit per inflorescence was lower than eight, which was not affected by the number of flowers on the inflorescence. It may indicate that the selective abortion of the fruit and seed is caused by the resource limitations, or is a reproductive strategy of V. unijuga that the redundant flowers are selectively aborted by the plants, suggesting that the actual seed yield of V. unijuga will be influenced by the selective abortion.