Objective To investigate the effects of serum containing substances of a Chinese traditional drug, Zuogui Pill, on expression of IL-1, IL-6 and COX-2 in osteoblasts, and to study the mechanism of action of Zuogui Pill treatment for osteoporosis. Methods Osteoblasts were obtained from newborn rats calvaria by collagenase-trypsin digestion. Three groups were included in the experiment: normal serum group, serum of ovariectomized (OVX) model group and serum of Zuogui pill-treated OVX model group. Immunohistochemical techniques were used to detect the expression of IL-1, IL-6 and COX-2. Results Expression of IL-1, IL-6 and COX-2 in osteoblasts in the serum of OVX model group was increased compared with that in the normal serum group, and their expression in the serum of Zuogui pill-treated OVX model group was significantly decreased as compared with those in serum of OVX model group, but did not show significant difference from those of normal serum group. Conclusion The serum containing Zuogui pill substances can inhibit the secretion of IL-1, IL-6 and PGE_2, which may be one of the mechanisms of action of Zuogui Pill treatment for osteoporosis.