Abstract: 【Objective】 The Y-strain chickens were obtained by crossing the E-strain cocks of Chahua No.2 with D-strain hens of Digao,and the N-strain chickens by crossing the Tengchong Snow Chickens with white flesh with D-strain hens of Digao. The growth performance of the two hybrid progenies was evaluated for the growth and development law of the most dominant hybrid progeny.【Method】 The Y-strain chickens and N-strain chickens born on the same day were selected as the research objects.After that,the body weight indexes of 0-29 weeks were measured,and the growth and development situations were recorded. At 60,90 and 120 days of age,30 cocks and 30 hens were randomly selected from Y-strain and N-strain chickens for the measurement of body weight and body size to compare the differences and correlations of the two breeds to determine the most dominant hybrid progeny. Three nonlinear growth models,Logistic, Gompertz and von Bertalanffy,were used for the curve fitting of the body weight of different hybrid progenies under different sexes to obtain the best growth curve model.【Result】 The weight growth curve of 0-29 weeks showed that the body weight of Y-straincocks was greatly better than that of N-strain cocks,and the body weight of Y-strain hens was slightly better than that of N-strain hens. The results of body weight and body size suggested that cocks were extremely significantly larger than hens(P<0.01) in Y-strain and N-strain chickens,and Y-strain chickens were obviously better than N-strain chickens under the same sex.Y-strain chickens with hybrid advantage were used for growth curve fitting analysis which demonstrated that the fitting value of von Bertalanffy was closer to the measured value. Thus, von Bertalanffy was the best growth curve model for the Y-strain chickens. Moreover,the analysis of body weight and body size showed that there was a high correlation between the body weight and shin girth of Y-strain chickens,and therefore shin girth could be used as a reference standard for Y-strain chickens breeding.【Conclusion】 The hybrid improvement result of Y-strain chickens obtained from the cross of E-strain cocks of Chahua No.2 with D-strain hens of Digao is better than that of N-strain chickens obtained from the cross of cocks of Tengchong Snow Chickens with white flesh and D-strain hens of Digao. And the growth curve fitting model of von Bertalanffy can more accurately reflect the growth and development law of Y-strain chickens,making it the best growth curve model of Y-strain chickens.