Keywords: 
• forest tree breeding /
• birch（Betula platyphylla） tetraploid progeny /
• multi-point test /
• family selection /
• genetic stability

Abstract: Multi-point testing of tree progeny, an important link in the study of tree suitability and stability, was used to determine the height and ground diameter of Betula platyphylla （birch） for six triploid families and four diploid families planted at four sites: Shangzhi, Huinan, Linghai, and Dandong. 3 years ago a multi-point conjoint analysis was used for differences in height between sites. Results of the multi-point conjoint analysis of height and ground diameter showed that differences in height between the sites were highly significant （P＜0.01）. Also, ground diameter for the Dandong and Linghai sites was significantly different （P ＜0.05）. Families 314 and 319 were excellent triploid families at the Shangzhi site; at Huinan they were 318 and 320; at Linghai: 314, 316 and 320; and at Dandong: 316, 318 and 319. Then, tested families were divided into three types according to their productivity index and genotype grouping methods. The first type included high yield-instability families 202, 314 and 320. 201, 318 and 319 belonged to the low yield-stability type. The low yield-instability type contained families 203, 204 and 315. Excellent families selected from all sites belonged to the first and second type. This study not only provided a reference for early popularization of birch triploid families, but also formed an important basis for alterations of high generation triploid seed orchards. ［Ch, 3 fig. 6 tab. 24 ref.］