The invention belongs to the technical field of oilfield development, and specifically relates to a temperature-resistant and salt-resistant type anti-swelling clay stabilizer and a synthetic method thereof. The temperature-resistant and salt-resistant type anti-swelling clay stabilizer is prepared through the following steps of enabling phthalic anhydride to react with n-octyl alcohol, thus generating n-octyl phthalic anhydride hemi-ester; carrying out a solution polymerization reaction on the n-octyl phthalic anhydride hemi-ester and 2-(dimethylamino) chloromethane hydrochloride, thus generating an intermediate; finally enabling the intermediate to react with benzyl bromide, thus generating the temperature-resistant and salt-resistant type anti-swelling clay stabilizer, wherein a molar ratio of the phthalic anhydride, the n-octyl alcohol, the 2-(dimethylamino) chloromethane hydrochloride and the benzyl bromide is 1 to 1.1 to 1.3 to 1.6. The temperature-resistant and salt-resistant type anti-swelling clay stabilizer disclosed by the invention has the characteristics that the sources of raw materials are wide, a synthetic technology is simple, the dosage is less, and the oil reservoir adaptability is strong; the temperature-resistant and salt-resistant type anti-swelling clay stabilizer is good in temperature resistance and salt resistance, the temperature resistance can reach 250 DEG C, the mineralization resistance degree can reach 200,000 mg/L, and good compatibility is obtained; the temperature-resistant and salt-resistant type anti-swelling clay stabilizer can be forcefully adsorbed to the surface of clay and is not easy to decompose, long in validity period and high in anti-swelling rate, and the anti-swelling rate can reach 98 percent or more.