Objective To study the biocompatibility and biological activity of hydroxyapatite (HA) with different strontium (Sr) contents. Methods The Sr doped HA (Sr-HA) materials containing 0%, 1%, 5%, 10%, and 20% Sr were prepared and the concentrations of Ca²⁺ and Sr²⁺ in the leaching liquor of them were determined in each group. Hemolysis tests were performed in vitro for the 5 materials. L929 fibroblasts were seeded and cultured with leaching liquor of materials for 2 d and 7 d; cell morphology was observed under microscope and the in vitro cytotoxicity of the five materials was detected by MTT assay. The MG63 bone cells were seeded on the surface of the 5 materials; then cell adhesion was observed at 1, 4, 12 h of culture, and the proliferation of cells was observed on day 1, 4 and 7 of culture by MTT method; and alkaline phosphatase (ALP) activity of the osteoblasts was detected on day 1, 3, and 5. Results The highest Ca²⁺concentration was found in the leaching liquor of 5% Sr group, and the lowest was found in the 1% Sr group; the highest Sr²⁺concentration was found in the leaching liquor of 20% Sr group, and the lowest was found in 0% Sr group. The hemolytic rates of Sr-HA materials were lower than 5% in all the five Sr-HA groups. The morphology of L929 fibroblasts in the five Sr-HA groups was similar to that of the negative control group; and MTT assay showed that the overall cytotoxicity of the five Sr-HA groups was grade 0 or 1. After 4 and 12 h culture, the number of adhered MG63 osteoblasts in 5%, 10%, and 20% Sr groups were significantly more than those in 0% and 1% Sr groups (P<0.05, P<0.01). On day 4 and 7 of culture, the proliferation rates of MG63 osteoblasts in 5%, 10% and 20% Sr groups were significantly higher than those in 0% and 1% Sr groups (P<0.05). The ALP activity of MG63 osteoblasts in 5% and 10% Sr groups was significantly higher than that in 0% and 1% Sr groups on day 3 of culture (P<0.05); and that in 5%, 10%, and 20% Sr groups was higher than that in 0% and 1% Sr groups on day 5 of culture. Conclusion Sr-HA material with different Sr contents has good biocompatibility; the combination with certain concentration of Sr can effectively improve the biological activity of HA, with the best activity seen when Sr ratio is 5% or 10%.