The growth characters of 15-year-old Space Mutation families of Betula platyphylla（HT-1， HT-2， HT-3， HT-4） and ground controls（CK-1， CK-2， CK-3， CK-4） were analyzed， and the growth characters of 2-year-old， 5-year-old and 15-year-old B. platyphylla were used to fit the growth curve. The results showed that the heights of 15-year-old HT-1 and HT-4 were significantly different from the ground control， respectively. The HT-1 height was higher than the ground control， while the HT-4 height was lower than the ground control. The heights of the other two families after Space mutagenesis were also higher than those of the control， but did not show a significant level. With the growing， some characters of the Space mutagenesis Birch families compared to the ground controls changed from significant differences to nonsignificant differences， but the overall trend of differences remained consistent with the seedling stage. The value of repeatabilities of the Space mutagenesis families and ground controls were high（>0.5）， except the 98-3 family. The favorable mutation on height trait of the HT-1 was the highest， which was 7.31%. Using