Objective To explore the possible mechanism of analgesic effect of Xinzhi Formula（ XZF）.Methods In total 70 SD rats were randomly divided into control group

model group and western medicine group（ tramadol hydrochloride

0. 01 g /kg）

XZF high dose group（ concentrated decoction of XZF

9 g /kg）

XZF normal dose group（ concentrated decoction of XZF

4. 5 g / kg）

XZF low dose group（ concentrated decoction of XZF

2. 25 g / kg） and TCM control group（ Wuling Zhitong Capsule

0. 06 g / kg）

with 10 rats in each. Except for the control group

all groups were injected with Walker256 ascites tumor cell suspension on the left hind tibia to establish bone cancer pain models. Fourteen days after modeling

corresponding medication was applied by gastric administration

once daily for 7 days. The expression of glial fibrillary acidic protein（ GFAP）

cluster of differentiation 11b（ CD11b） mRNA

nuclear factor-κB（ NF-κB） in spinal cord tissue from L4- L5 of the rats was detected. Results There were much more GFAP positive cells in the model group than that in the control group and XZF normal dose and high dose groups. The expression of CD11 b mRNA in the model group was significantly higher than that in the western medicine group

and XZF normal dose and high dose groups（ P < 0. 01）

but there was no significant difference among treatment groups. The expression of NF-κB in the model group was higher than that in the control group

and the expression of NF-κB in the XZF high dose group was significantly lower than that in the model group（ P <0. 01）. Conclusion The mechanism of analgesic effects of Xinzhi Formula on rat model of bone cancer pain may be related to the inhibition of cell proliferation and activation in the spinal glial cells and down-regulating of NF-κB proteins.