In this report, the process of hybridization between different ploidy levels was observed in rice. Autotriploid (2n = 36) 149-B, generated naturally from the twin-seedling rice population SAR-2, was used as the female parent crossing with a normal diploid variety Shuhui 363. The processes of fertilization and embryological development were investigated. The pollen could germinate in triploid tissue of pistil normally and arrive at micropyle. But the percentage of double fertilization was only 8.89%, and the percentage of seed setting was 0.566%. The hybridization obstacles mainly occurred in the process of fertilization. Barriers of double fertilization, prolongation and abnormal development of proembryo, and even development stopping or differentiation failure of embryo and/or endosperm could result in abnormal development and abortion of zygote.