‘Dongshi Zaoyou’ pummelo and its hybrid offsprings，methods including magenta acetate staining and aniline blue staining，cross-pollination，and molecular markers were used to study the mechanism of seedlessness in ‘Dongshi Zaoyou’ pummelo.The results showed that the floral structure of ‘Dongshi Zaoyou’ pummelo was intact，with pollen vitality and germination rates of 94.80% and 86.20%，respectively.The self-pollination of ‘Dongshi Zaoyou’ pummelo showed incompatibility，while cross-pollination with ‘Shatianyou’ pummelo showed compatibility.A total of 164 F₁ hybrids were identified from 175 hybrid offsprings of ‘Shatianyou’ pummelo × ‘Dongshi Zaoyou’ pummelo with S₅/S₆ molecular marker genotyping，ruling out the possibility of male sterility in ‘Dongshi Zaoyou’ pummelo.The results of observation for two consecutive years showed that the mean fruit setting rates of stimulating parthenocarpy and natural parthenocarpy in ‘Dongshi Zaoyou’ pummelo was 13.04% and 25.56%，respectively.It is indicated that the main reason for the seedless development of ‘Dongshi Zaoyou’ pummelo is its self-incompatibility and certain ability to produce parthenocarpy.