A new flocculant with cationic microblock structure was prepared by using template polymerization. Acrylamide (AM) and acryloyloxyethyltrimethylammonium chloride (DAC) were used as monomers, and sodium polyacrylate was used as the template. The reactivity ratio, H-1 NMR, C-13 NMR, and thermogravimetric analysis were employed to characterize the structural properties of products. Results show that, with the addition of the template, the reactivity ratio of DAC increased, whereas that of AM decreased. Evident microblock structure was synthesited in copolymers when the molar ratio of template to DAC was 1.0. Activated sludge dewatering experiment results reveal that the cationic microblocky flocculant exhibited superior dewatering efficiency, and a low moisture content of 71% and a specific resistance of 1.99 X 10(12) m.kg(-1) were acquired at pH 7.0 and a 40 mg L-1 dosage. The enhanced charge neutralization and bridging effect of the cationic microblocky flocculant contributed to the formation of floc with a large size and compact structure.