Abstract: Fertilization, embryo development and origin of twin-embryo of autotetraploid rice with twin-embryo seedlings(ARTS) were observed and verified. The research results showed that there were no big difference in time of beginning fertilization between autotetraploid and diploid rice. ARTS had obvious specificities in fertilization and embryo development. The embryological witnesses of the twin-embryo seedling character in ARTS were found. The embryological reasons of producing the twin-embryo seedling related to the 4 factors, including the twin-embryo sacs, the fertilization of the egg and the similar egg, the specific antipodal cells, the endosperm cells. ARTS expressed weaker in sexual reproduction and bigger variability in genetics, showing its potential values in ion beam mediated technique.