Abstract: Objective To investigate the effect of norcantharidin on bone metastasis of human small cell lung cancer(SCLC). Methods A skeletal metastasis model of SCLC was established by injecting NCI-H446 cells into the right leg of nude mice. Sixty male health BALB/C mice were divided randomly into 3 groups including control group，high-dose group and low-dose group. The effects of norcantharidin on bone metastasis and bone metabolism were investigated by X-ray，pathological and   molecular biochemical detections，while the conditions of tumor growth were observed. Results Comparing to drug groups，the control group were with faster tumor growth，larger tumor size，and lower total weight gain at the end of the experiment. The levels of serum PICP and PINP were higher in control group，but which were not statistically different from that of the drug groups. Conclusions Norcantharidin can inhibit bone metastasis of lung cancer. Serum PICP and PINP levels can be used for early diagnosis and treatment monitoring of bone metastasis of SCLC.

Key words: Skeletal metastasis, Nude mice, Models, Norcantharidin