The possible biochemical mechanism of gallium was studied in this paper. One-day-old hens were fed to up to 68 weeks on a control diet and diets containing gallium. Serum calcium and phosphorus, serum alkaline phosphatase, tartrate resistant acid phosphatase (TRAP), serum osteocalcin, homocysteine, C-terminal crosslinked telopeptides of collagen type I, and bone mineral content were measured, respectively. The beneficial effects of gallium supplementation on improvement of cage layer osteoporosis were attributable mainly to decrease TRAP activity, C-terminal crosslinked telopeptides of collagen type I level, plasma calcium and phosphate concentrations, and increase the mineral content in the bones and osteocalcin level in plasma.