Abstract: In order to establish genetic improvement foundation of Toona sinensis, a seedling raising tests in a light medium container were conducted by using 45 Toona sinensis elite and half-sib families progenys in Sichuan, and investigations were made on the growth condition of seedling height and ground diameter. The result showed that there were extremely significant differences in both seedling height and ground diameter among families, which showed good selecting and breeding potentiality for their abundant variation among half-sib families. After statistically analyzing, 4 fast-growing improved families in seedling period of Toona sinensis were screened out, by the name of No. 19, 18, 24, 8 of Pengxi. The average seedling height and ground diameter of 4 fast-growing improved families were 29.92 cm and 4.18 mm respectively, which were higher by 28.83% and 9.51% than the average figure of 23.22 cm and 3.82 mm of the 45 tested families, respectively, and the genetic gains were 23.59% and 7.99%, respectively. However, the growth performance in the seedling period could not demonstrate the growth law during whole life time but could help researchers finish early selection of selecting and breeding of Toona sinensis improved families.