-Tricalcium phosphate (-TCP) is an ideal bone repairing biomaterial because of its biocompatibility and biodegradability. Microwave irradiation provides rapid and homogeneous energy throughout the volume, which makes it possible to get smaller and uniform particles. Magnesium (Mg), as an indispensable element in human body, plays an important role in osteogenesis. The aim of this work was to explore the influence of microwave irradiation time and temperature on Mg-doped -TCP (Mg-TCP) synthesis. It was found that smaller and more homogeneous particles were obtained after microwave irradiation. On the other hand, microwave irradiation increased the defects in crystal grains and caused agglomeration of particles. According to the characterization results, the microwave operation parameters were determined as 40 degrees C and 20min. Then -TCP with different Mg substitution contents (0, 5, 10 and 14mol%) were synthesized in the parameters. The results revealed that Mg was incorporated into -TCP as designed and the substitution did not change the phase structure notably except for reducing of cell parameters and lattice volume. Osteogenesis in vitro was performed on bone marrow mesenchymal stem cells of rats to discuss the influence of Mg-TCP on cells proliferation and differentiation. It was found that Mg14-TCP showed the best facilitation on proliferation and differentiation, and the promotion effects of Mg5- and Mg10-TCP were suppressed by deposition of the ions dissolved in medium on ceramic samples.