Abstract: OBJECTIVE To prepare paclitaxel in situ gel and to investigate its physical and chemical properties and effect on bone metastasis of tumor in vivo. Methods Paclitaxel in situ gel was prepared by cold solution method, and its stability and release characteristics in vitro were investigated. The MRMT-1 cell model of breast cancer bone metastasis in nude mice was established to study the effect of anti-bone metastasis of tumor of paclitaxel in situ gel in vivo by local administration in tumor. Results The gelation temperature of paclitaxel in situ gel was 32.3 ℃, and the drug release curve in vitro was Q=2.557 9t+ 28.067, r=0.999 5, which fit the zero-order kinetics equation. Animal experiment results showed that paclitaxel in situ gel could effectively reduce tumor volume in nude mice, the inhibitory effect was positively correlated with the dosage. X-ray examination showed that bone damage of nude nice was severe in the blank gel group, and bone damage of nude mice was significantly improved after of paclitaxel in situ gel administration. Compared with the blank gel group, bone density was also significantly increased in nude mice in the high concentration of paclitaxel in situ gel group(P<0.05). Conclusion The paclitaxel in situ gel prepared in this study has good release characteristics in vitro, and can significantly inhibit tumor bone metastasis and improve the bone damage caused by tumor.