A new type of composite bone cement was prepared and investigated by adding calcium silicate (CS) to calcium phosphate cement (CPC). Low-crystalline CS prepared by heat treatment at low temperature had excellent bioactivity and degradability. Adding CS to CPC did not affect the phase composition and chemical structure of CPC, and had a little effect on the setting time and compressive strength of the composite cement. CS could effectively improve the in vitro and in vivo bioactivity of CPC, and enhance the cell proliferation on the CPC material. The introduction of CS is an effective way to improve the bioactivity and degradability of CPC, which will provide a new strategy to modify CPC.