The invention relates to a synthetic method of water-in-water cationic polyacylamide emulsion. The synthetic method is characterized by mixing inorganic salt, non-ionic hydrophilic monomers, anionic monomers, hydrophobic monomers, functional monomers having surface activity, a stabilizing agent, a chelating agent and deionized water, adjusting the pH value to be between 6.5 and 7.5, uniformly emulsifying the mixture by an emulsifying machine, introducing nitrogen for protection, adding an evocating agent at twice at the temperature of 18 to 50 DEG C, carrying out second polymerization reaction for 1 to 3 hours after 4 to 7 hours of the time of first polymerization reaction and making the emulsion product.