Concrete is a building material known for its high compressive strength but susceptibility to cracking. Once concrete cracks, moisture, aggressive ions, and air can easily penetrate its body, deteriorating its mechanical properties and durability. Herein, polyacrylamide (PAM) is incorporated into the concrete via in situ polymerization of acrylamide (AM) to construct a polymer-cement network, aiming to improve flexural strength and crack resistance. Incorporating 7 % AM, the initial cracking fracture toughness is increased by 47.5 %. Concrete with 10 % AM exhibits a 28-day flexural strength of 19.38 MPa, 65.5 % higher than normal concrete. The polymer network formed by in situ polymerization of AM crosslinks with cement hydrates to construct the polymer-cement network, which is responsible for the improvement of flexural strength and crack resistance. Upon completion of the polymerization reaction, the aggregate and the cement matrix are bridged by polymer, concomitant with the densification of the interfacial transition zone (ITZ). In situ polymerization of AM is found to be more efficient and effective than directly adding PAM in improving flexural strength. Moreover, refinement of the pore structure is also observed by in situ polymerization of AM. In conclusion, our study presents a convenient and efficient approach to improving the crack resistance of concrete, thereby spurring the development of high performance concrete.