Karyotype of six species and subspecies in genus lemur(Eulemur) were analyzed comparatively. All the metacentric chromosomes in each (sub)species were composed of same chromosome arms but the combination mode of arms for metacentric chromosomes in each (sub)species were totally different besides two haploid chromosomes which are identical in all six (sub)species. Speciation mode of these species is proposed. In genus Eulemur, hybrid of Eulemur fulvus fulvus and Eulemur macaco macaco was formed and produced equilibrated new-gametes which are formed by centromeric fusion followed circular form arrangement at pachytene stage. In circular form arrangement due to centromeric fusion, the chromosome members can be combinated differently to form another circular arrangement. Some of many circular forms can give fertile new gametes corresponding to the haploid karyotype of pre-species. When new gamete fertilized with the same type of gamete to produce new homozygote (pre-species), additional chromosomal rearrangements were followed to produce karyotypes of existing Eulemur species. Due to these complementing rearrangement, each new species are differentiated from their ancestral species.