Provided are a metallic crosslinking coagent, preparation methods thereof, and a resin composition comprising the metallic crosslinking coagent. With the active-hydrogen containing organic phosphorus compound group and metallophilic acrylate group, the metallic crosslinking coagent provides both stabilizer and flame-retardant effects, enhances the crosslinking efficiency of the resin composition, and improves the compatibility between flame retardant and the polymer. Accordingly, the metallic crosslinking coagent is effective to improve the mechanical properties of the application material and to develop a safe and environmentally friendly flame retardant material.