Ultraviolet (UV)-initiated template polymerization (UTP) was used as a feasible strategy to prepare a novel anionic polyacrylamide (APAM) with a microblock structure. In the template copolymerization system, acrylamide (AM) and sodium allylsulfonate (SAS) were used as monomers, and poly (allylammonium chloride) (PAAC) as a template. The chemical properties of the polymers were observed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), ¹H (¹³C) nuclear magnetic resonance spectroscopy (¹H (¹³C)), and thermogravimetry/differential scanning calorimetry (TG/DSC). Results showed that the novel anionic microblock structure was formed in the template copolymer. Besides, the results of the association constant (K_M) indicated that the copolymerization followed I Zip-up (ZIP) template polymerization mechanism, which indicated the formation of the microblock structure again. Parameters such as pH and dosage that affected the flocculation performance, flocculation kinetics and the FTIR spectra of the generated flocs were investigated to further observe the effect of anionic microblocks on flocculation performance and understand the relationship between the flocs and flocculants. Flocculation experimental results demonstrated that the anionic microblocks in the template copolymer could enhance the charge neutralization and bridging ability, and therefore an excellent flocculation performance of treating high turbidity water was observed.