Concrete as an artificial stone owns the weakness of high brittleness and poor flexural strength, dramatically restricting its potential. Therefore, it is crucial to reduce the brittleness and increase the flexural strength of concrete to prolong its service life. Herein, we developed a cement composite with low hydration temperature and high mechanical strength (especially in flexural strength) by combining Field's metal with in situ polymerization of acrylic acid (AA) and acrylamide (AM). A cement composite with compressive and flexural strength increased by 8.2% and 174.2% was achieved by tuning the dosage of Field's metal and AA-AM copolymer. The hydration temperature was significantly reduced with the assistance of Field's metal and AA-AM copolymer, inhibiting the formation of the thermal crack. In situ polymerization of AA and AM monomers was responsible for improving the intrinsic toughness of cement hydrates by constructing a polymer-cement network, significantly enhancing flexural strength. The in situ polymerized AA-AM copolymer acted as a bridge between Field's metal and the cement matrix, improving their interface and contributing to the increased mechanical strength. The filling effect of Field's metal and AA-AM copolymer refined the pore structure of the composite as well. Overall, our findings may offer a promising strategy for developing more robust, resilient, and sustainable cementitious materials.