Abstract: 252 families of GIFT strain tilapia were established using nested homogeneous random matching method and 106 P1 families were collected.The success rate of matching was 42.06%.By standardized rearing,86 full-sibfamilies of GIFT strain tilapia were obtained ultimately,including 10 half-sibfamilies.22 families were selected under the hatching time,and their growth wasstudied simultaneously.The results showed that very significant differences werefound between the averages of body length and body weight in different families of the same age.Further multiple comparisons showed that the sequence of phenotypic values of body length and body weight existed inconsistency in different families of different age.The growth rate of each family was very different at different age,but the G2,G4,G6,G12 and G22 family remained relatively stable.Theanalysis for body weight of 150 d tilapia showed that the biggest family is G6,the mean of body weight is 815.50 g,the coefficient variation of tilapia population(18.08%) is much larger than the mean of the families,the family G6 had the least CV(10.70%),and family G8 had the max CV(18.42%).

Key words: Oreochromis niloticus, family, growth