In-situ polymerization modified cement paste shows a great potential in 3D concrete printing (3DCP) due to its enhanced rheological properties. Unlike direct adding conventional polymer, how in-situ polymerization and cement hydration synergistically regulate the rheology of cement paste with different monomer dosages remains unclear. Here, we investigate the rheological properties of in-situ polymerization modified cement paste with different dosages of sodium acrylate (SA) to reveal the roles of cement hydration and polymerization. When the monomer dosage is lower (1 % and 3 %), the polymerization inhibits the cement hydration without providing sufficient contribution to the structural development of cement paste, resulting in the decreased rheological properties, such as static/dynamic yield stress and structural build-up rate. On the contrary, once the monomer dosage reaches a higher level (5 % and 7 %), the resultant polymers can gradually form a network interwinding within the cement particles, thus leading to enhanced rheological properties, regardless of the more severely inhibited cement hydration.