Objective To explore the ectopic osteogenesis introducing ability of recombinant human bone morphogenetic protein-2/chitosan/dextran sulfate composite microspheres and recombinant human bone morphogenetic protein-2/chitosan composite microspheres on SD rats. Method 36 SD rats were randomly divided into three groups, in which the quadriceps muscle bag model of the rats were established; the bags were implanted respectively with rhBMP-2(group A), CS/DS microspheres (group B), and rhBMP-2/CS/DS microspheres (group C). Hardness of the implanted regions tissuesat the 4th,8th,12th weekend were observed, and four rats were sacrificed in each group, from which the ectopic bone tissues were harvested. The bone formation situation of plantation areas were generally observed, and the heterotopic ossification organization tissues were scanned by micro-CT, and were three-dimensionally reconstructed by using the Mimics software;parameters such astissue bone volume fraction (BVF), trabecular thickness (Tb.Th), bone mineral density (BMD) were detected; Some heterotopic ossification organization tissues were taken for histological observation and analysis of ALP activity and calcium content. Results At the 4th weekend, tissues around implanted regions of each group had slightly harder texture, and there was no significant difference among the three groups; at the 8th and 12th weekend, hardness of tissues around implanted regions of each group increased significantly, and the group C had harder tissues formed than group A and B. At the 4th weekend, HE staining showed that the three groups had a small amount of bone tissue formation, but not obviously; the BVF, Tb.Th, BMD, ALP activity and calcium levels of B, C groups were significantly higher than group A; there were no statistically significance on the above indicators of group B and C. At the 8th and 12th weekend, gradually-increased and marture bone tissues could be seen in the three groups under HE staining. However,there were more mature ectopic bone tissues in group B and C than group A; And the bone tissues of group C were more mature than group B. Meanwhile, the BVF, Tb.Th, BMD, ALP activity and calcium levels of group B and C were significantly higher than group A, and the above-mentioned indicators of group C were higher than that of group B. Conclusion rhBMP-2/CS/DS microspheres have stronger ability of inducing ectopic bone than rhBMP-2/CS microspheres and single rhBMP-2, and it mayhave good prospects for applicationin bone tissue engineering.