The chromosome number and karyotype of 5species in east aisa region of Alnus was studied by shedding cell wall and dialysis methods.The results showed that the karyotypes among them were not distinct and most chromosomes were metacentric or submetacentric.The chromosome number of A.nitida was 28,the karyotype formula was K2n=28=22m 4sm(2SAT) 2st(2SAT);2n=42 and K(2n)=42=36m 6sm for A.hirsuta;2n=56 and K(2n)=56=2M 40m(1SAT) 14sm(1SAT) for A.cremastogyne;2n=56 and K(2n)=56=46m 8sm 2st for A.formosana;2n=112 and K(2n)=112=80m 28sm 4st for A,firma.