Objective: To explore the physical and chemical properties of hydrolyzed egg yolk powder and its effect on the growth of long bone in SD rats， and to clarify the necessity of developing hydrolyzed egg yolk powder. Methods: the relative molecular weight distribution and amino acid composition of EYP and EYH were determined by high performance gel filtration chromatography and high performance liquid chromatography； The growth promoting activity of long bone in growing rats was compared， and the basic growth indexes， bone length and bone index， bone biomechanics and biochemical indexes in serum were measured. Results: the relative molecular weight distribution showed that the total proportion of peptides < 1 000 u in EYH was 88.97%； The determination of amino acid composition showed that the proportion of 7 kinds of amino acids that can increase bone mineral density in EYH was higher than that in EYP； The results of animal experiments showed that the intervention of EYP and EYH could promote the increase of bone length and bone index， and the promotion effect of EYH on bone length and bone index reached a significant level， increased by 2.06% (P<0.05) and 9.42% (P<0.05)， respectively， which was better than EYP； The results of bone biomechanical experiments showed that EYP and EYH could significantly increase the bending strength and elastic modulus of femur. Compared with CON group， the EYH treatment group increased by 38.56% (P<0.05) and 52.14% (P<0.05)， and the EYP group increased by 32.51% (P<0.05) and 42.63% (P<0.05)， respectively. In contrast， the EYH group increased more， indicating that it has better ability to strengthen bones and increase toughness； The determination of biochemical indexes in rat serum showed that the content of PINP in EYH group was 18.86% higher than that in CON group (P<0.05)， and 13.27% higher than that in EYP group (P<0.05). TGF-β1 is an important growth factor to promote bone formation. Compared with CON group， the content of TGF-β1 in serum of EYH group and EYP group increased by 52.25% (P<0.05) and 26.68% (P<0.05)， respectively. GH/IGF-1 axis plays an important role in regulating growth and metabolism， and can promote bone growth. Compared with CON group， the serum GH content in EYH group and EYP group increased by 22.32% (P<0.05) and 12.64% (P<0.05) respectively， and the serum IGF-1 content in EYH group increased by 5.04% and 17.20% (P<0.05) respectively compared with CON group and EYP group. EYP can increase the contents of TGF-β1 and GH in serum， while EYH has a more significant ability to increase the contents of TGF-β1， GH and IGF-1 in serum of rats， at the same time， it can increase the content of PINP， a marker of bone formation， and reduce the content of CTX-I， a marker of bone resorption.