The invention discloses a dispersible flocculant, a preparation method and application thereof. The preparation method comprises the following steps: completely dissolving an acrylamide monomer, a dimethyl diallyl ammonium chloride monomer, poly dimethyl diallyl ammonium chloride and inorganic salt with deionized water, stirring in a 40 to 65 DEG C thermostatic waterbath, adjusting the pH value ofa reaction system to be 3 to 8, leading nitrogen for protection, adding a composite initiator K2S2O8-NaHSO3-V50, and ensuring that reaction is performed at 40 to 65 DEG C in nitrogen atmosphere, so as to obtain a cationic polyacrylamide dispersible flocculant. In dispersible cationic polyacrylamide (CPAM) dispersoid, the relative molecular weight of the cationic polyacrylamide polymer is high, the viscosity of the dispersoid is low, and the stability is high.