An injectable composite bone cement was fabricated by employing Sol-Gel derived mesoporous borosilicate bioactive glass spheres (MBGS) as solid phase and sodium alginate (SA) solution as liquid phase. The effects of the B₂O₃/SiO₂ ratio in MBGS on its textural properties and workability, compressive strength and bioactivity of bone cement were characterized. It is found that with the increase of boron content, the specific surface area of MBGS increases from 161.71 m²/g to 214.28 m²/g, and the average pore size and total pore volume also increase, which accelerates the Ca²⁺ release and rapidly crosslinks MBGS and SA. Thus, the workability, mechanical property and in vitro mineralization of bone cement are significantly improved, as the setting time is shortened from 21 min to 9 min and the compressive strength is enhanced from 3.4 MPa to 4.1 MPa. Comprehensive performance of all aspects, BC-30 bone cement showing good workability, mechanical properties and in vitro mineralization ability, displays the optimal component. Therefore, improving the textural properties of MBGS is an effective method to enhance the workability, compressive strength and bioactivity of composite bone cement.