Abstract: Objective To explore the analgesia effects of quinpirole（QNP） via intrathecal injection and its influence on spinal microglia activation in rats with bone cancer pain. Methods Sixty adult male SD rats were used to establish bone cancer pain model by intra-tibia inoculation of Walker256 mammary gland carcinoma cells. The rats with bone cancer pain were randomly divided into 3 groups： high-dose QNP （QNP-H） group， low-dose QNP （QNP-L） group and normal saline （NS） group, with 20 rats in each group. QNP-H group and QNP-L group received intrathecal injection of 10μl QNP at the dose of 10 and 5μg/kg，respectively. Another 20 male SD rats were chosen as control （C） group and received the same volume of saline as NS group. Pain behaviors were assessed before treatment and 1，3，5 and 7d during treatment to analyze the paw mechanical withdrawal threshold （MWT） and paw withdrawal thermal latency （WTL）. The immunohistochemistry was employed to evaluate the spinal microglia number ionized calcium binding adaptor molecule 1 and activation by the integral optical density （IOD） of C3 complement receptor （OX-42） and cannabinoid receptor 2 （CB2）. The spinal levels of TNF-α and IL-1β were measured by enzyme linked immunosorbent assay. Moreover， the protein levels of spinal Toll like receptor4 （TLR-4） and its receptor2 （TLR-2） were detected by Western blotting. Results Compared with C group，there were lower MWT and WTL, but higher spinal microglia number, IOD of OX-42 and CB2, TNF-α, IL-1β, TLR-2 and TLR-4 in NS, QNP-L and QNP-H groups with significant difference （P＜0.05）. Intrathecal injection of QNP improved the above abnormalities of rats with bone cancer pain compared with NS group （P＜0.05）. The effect of QNP-H group was stronger than that of QNP-L group（P＜0.05）. Conclusion Intrathecal injection of QNP exhibits a good analgesic effect on bone cancer pain and inhibits spinal microglia activation and inflammatory reaction.