A template assembly method was introduced to obtain a cationic hydrophobic micro-block structure based amphiphilic electrolyte poly(acrylamide-co-2-methacryloxyethyltrimethyl ammonium chloride) P(AM-DMC) in this work, thereby increasing charge density and enhancing charge neutralization ability at the same charge density. The alteration of copolymerization or homo-polymerization was evaluated by the changes in reactivity ratios, so as to unravel the mechanism of template assembly. The micro-blocks generated by the new distribution of sequences were demonstrated by ¹H nuclear magnetic resonance spectroscopy (¹H NMR) and differential thermal-thermogravimetric analysis (DSC-TGA). Two negative controls were employed in sludge dewatering experiments to further evaluate the advanced properties of the template-assembled polymer. The results further verified that the positive effect of template assembly on flocculation performance of the polymer was achieved mainly through two ways: improving charge density and generating the micro-block structure. It can be concluded that the introduction of template assembly into polymerization can improve the performance of the polymer.