A series of cationic surface active monomers of acrylamide are prepared using a kind of polymerizable acrylamide monomer with brominated alkanes of different carbon chains as materials so as to changing the length of carbon chain of hydrophobic group. The product was identified by IR and 1H⁃NMR. The critical micelle concentration (CMC) and surface tension at CMC value (γCMC) was measured with methods of surface tension and conductibity measures; the solubility of surfactants (AMQC8,AMQC12, AMQC16) was determined by UV spectrophotometry at the same time. The experiment results show that with the growth of hydrophobic carbon chain, critical micelle concentration (CMC) was decreased gradually; the trend of Krafft temperature was gradually rising.