Abstract:In order to select superior families for breeding large-size diameter of Chinese fir (Cunninghamia lanceolata), the diameter at breast height (DBH) of 28 half-sib progenies in second-generation seed orchard of Guangdong were continuously determined at 4, 9, 11, 16 and 21 years old, compared with 2 control families from primary seed orchard and 1.5 generation seed orchard of Guangdong. The result showed that DBH of Chinese fir had significant difference (P<0.01) among families at the same age, and the phenotypic and genetic coefficient ranged from 4.43% to 6.29% and from 2.95% to 3.62%, respectively. The family heritability of DBH increased from 0.3359 at 4 years old to a peak of 0.5486 at 16 years old, and then became stable at 21 years old. The genetic correlation of DBH at 9 years old was close to that at 4, 11, 16 and 21 years old, respectively. So, according to multi-year breeding values and the ratio of diameter-grade volume of family at age of 21, three families (F5, F9 and F21) were selected as the superior families for large-size timer cultivation.