Abstract: Haploid plants obtained by the in vitro anther culture were planted in the experimental plot.The anthers were collected from a hybrid between Populus simonii,P.nigra and P.berolinensis Dippel.After planting the number of chromosome of the haploid plant was examined under microscope for four times within 8 years.It was revealed that the plants had gradually changed their tissues into those dominated quantitatively by diploid cells from chimera dominated by haploid cells. The number of chromosome was doubled at the age of 7—8 years and the plants became completely diploid ones.