Brushite calcium phosphate cement (brushite CPC) is a prospective bone repair material due to its ideal resorption rates in vivo. However, the undesirable mechanical property and bioactivity limited its availability in clinic application. To address this issue, incorporating polymeric additives has emerged as a viable solution. In this study, poly(ethylene glycol) dicarboxylic acid, PEG(COOH), was synthesized and employed as the polymeric additive. The setting behavior, anti-washout ability, mechanical property, degradation rate, and osteogenic capacity of brushite CPC were regulated by incorporating PEG(COOH). The incorporation of PEG(COOH) with carboxylic acid groups demonstrated a positive effect on both mechanical properties and osteogenic activity in bone repair. This study offers valuable insights and suggests a promising strategy for the development of materials in bone tissue engineering.