Cationic polyacrylamide (CPAM), is often used asflocculantin water treatment and sludge dewatering. CPAM prepared with traditional methods can’t react completelydue to the randomly-scattering cationic units in its molecules, resulting in its flocculation efficiency decline. So this study tried to use a novel method to prepare CPAM, i. e., acrylamide (AM) and diallyldimethylammonium chloride (DMDAAC) selected as monomers and poly sodium polyacrylate (PAAS) with two different molecular weights selected as the template, the template polymers (TPDA1 and TPDA2) were polymerized with ultraviolet (UV)-initiated template polymerization. The common polymer (NTPDA) of AM and DMDAAC was also polymerized through UV -initiated synthesis for comparison. All polymers were characterized with Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (1H NMR) spectroscopy and scanning electron microscopy (SEM), and used to sludge dewatering experiment. The spectrum analysis revealed that the template addition improved the reactivity ratio of DMD, as a result, the micro-block structure with DMDAAC continuous distribution were generated in polymer molecules, which improved the flocculation performance of polymer, especially charge neutralization; the SEMresult showed TPDA1 and TPDA2 both had a higher specific surface area and fractal dimension than NTPDA； the sludge dewatering experiment proved template polymers possessed preferable dewaterability and more permissive pH condition for application; In the optimal conditions of TPDA1 dose of 50.0 mg·L-1 and wastewater of pH 8, the sludge moisture content dropped to the lowest level of 72.5%. The molecular weight of template also had influence on polymer properties, and the template with smaller molecular weight had preferable dewaterability.