Abstract:The present paper recognized that according to the morphology comparison autoallopolyploid Sequoia sempervirens with genomic formula AAAABB[3] may originate from the hybridzation between romeone ancient species of Metasequoia and Sequoiadendron which were the parents. Metasequoia glyptostroboides and Sequoiadendron giganteum were direct descendants of the parents probably, which proyided gcnomes AA and B for S. sempervirens res- pectively.The concluson was the same as that based on the karyotypic data[19], but did not agree with Stebbins‘ inference that another ancestor,except Metasequoia, was extinct and did not left any close relatiyes.