Abstract: Objective:The effects of lactoferrin (LF) on bone health in juvenile rats were studied. Methods:Forty male Sprague-Dawley rats aged 4 weeks were randomly divided into control group (0 mg/kg bw/day), low dose LF group (100 mg/kg bw/day), LF medium dose group (500 mg/kg bw/day) and LF high-dose group (1000 mg/kg bw/day), continuous feeding for 30 days, the changes of body weight, visceral ratio, bone mineral density (BMD), bone microstructure of femur, levels of anti-tartrate acid phosphatase (TRACP), matrix metalloproteinases 9 (MMP-9) and cathepsin K (CTSK), nuclear factor kappa B receptor activating factor activating factor ligands (RANKL), osteoprotegerin (OPG) and OPG/RANKL in serum and bone marrow tissues of femurs in juvenile rats were measured. Results:After 30 days of LF gavage, compared with the control group, the increasing trend of body weight and visceral ratio of juvenile rats in LF dose group were similar that the difference was not significant (P>0.05), BMD, trabecular bone number (Tb.N), trabecular bone thickness (Tb.Th), the levels of OPG and OPG/RANKL in serum and bone marrow tissue of juvenile rats in medium and high dose group significantly increased (P<0.05), and Trabecular bone space (Tb.Sp) significantly increased, TRACP, MMP-9, CTSK and RANKL significantly decreased (P<0.05).Conclusion:Supplementation of LF can reduce bone resorption, increase bone formation and bone mass, regulate bone metabolism balance and promote bone health in juvenile rats.