The invention provides a composite initiator of a hydrophobic associated polymer and a preparation method of the hydrophobic associated polymer. The composite initiator is prepared from the following raw materials in parts by weight: 1-10 parts of potassium persulfate, 1-10 parts of ammonium persulfate, 0.5-5 parts of dibenzoyl peroxide, 1-10 parts of sodium hydrogen sulfite, 1-10 parts of sodium sulfite, 0.1-1 part of triethanolamine, 0.5-5 parts of urea, 0.5-5 parts of thiourea, 0.05-0.5 part of azodiisobutyronitrile and 0.05-0.5 part of azobis(isobutylamidine hydrochloride). The method comprises the following steps: a sequentially adding disodium ethylenediamine tetraacetate, sodium formate, lauryl sodium sulfate, acrylamide, AMPS-Na and DiC8AM to deionized water under a magnetic stirring condition, and fully stirring evenly; b introducing high-purity nitrogen into a mixed solution obtained from the step a, adding the composite initiator, and polymerizing to obtain hydrophobic associated polymer gel; and c coarsely crushing the hydrophobic associated polymer gel obtained from the step b, adding sodium hydroxide, hydrolyzing, drying in a blast drying oven, drying and crushing to obtain the product.