The development of injectable calcium phosphate cements (ICPC) represents a promising approach for minimally invasive surgical techniques. However, the undesirable anti-washout property and slow setting time of ICPC greatly hinder its clinical application. Xanthan gum (XG) has strong hydrophilic, shape retention and rheological properties. In this study, a fast setting and anti-washout injectable calcium-magnesium phosphate cement (fa-ICMPC) was developed by introducing XG, as an anti-washout agent, and magnesium phosphate cement (MPC) into calcium phosphate cement (CPC). The bone-regenerative capacity and the bioresorption of the fa-ICMPC were also investigated by injecting it directly into a rabbit thigh bone defect. The result showed that XG imparted anti-washout properties to the fa-ICMPC and enhanced the injectability of the fa-ICMPC. With the protection of thick viscous films formed by XG, the setting of the fa-ICMPC was not disturbed but accelerated due to the synergistic effect of MPC. The result demonstrated that fa-ICMPC was not crumbled and could fill the defects tightly. The newly-formed bone tissue grew into fa-ICMPC along with the degradation of the materials. In short, the fa-ICMPC exhibited potent anti-washout properties, fast setting, improved injectability, good biodegradability and osteoconductivity, and has the potential to repair bone defects by minimal invasive treatment.