Abstract: Owing to the absence of genetic recombination and the accumulation of deleterious mutations,unisexual animals were generally thought to be short-lived on an evolutionary timescale because of Mullers ratchet.However,more than 50 unisexual species have been identified in lower vertebrates and the evolutionary history has been revealed to be very long.The intriguing contradiction between the deleterious mutation accumul ation and the evolutionary longevity,and the underlying mechanism in the absenc e of genetic recombination remain to be revealed and interpreted.In this review,we introduce special structural characterization of genome,evolutionary history and possible ways to evolutionary success in these unisexual animals,such as mutation,triploidy allogynogenesis and reproduction mode diversity.