The improvement of red clay was carried out by using kaolinite to improve the engineering properties of red clay. The effect of the modulus of the alkali exciter and the amount of the geopolymer on the unconfined compressive strength and permeability coefficient of the improved red clay was analyzed, and the dry and wet cycle tests of the improved red clay with the optimum modulus of the alkali exciter were carried out to analyze the extent of damage to the improved red clay by different dry and wet cycles of the alkali exciter. The test results showed that the unconfined compressive strength of the improved red clay tended to increase and then decrease with the increase of the modulus of the alkali exciter, and was greatest when the modulus of the alkali exciter was 1.2; the greater the dose of the geopolymer, the greater the unconfined compressive strength of the improved red clay; the kaolin geopolymer could effectively reduce the permeability coefficient of the red clay, and the permeability coefficient of the improved red clay was the smallest when the modulus of the alkali exciter was 1.2, and the decrease was the greatest. The higher the number of wet and dry cycles, the lower the unconfined compressive strength of the modified red clay and the greater the damage, and after 12 wet and dry cycles, the strength damage of the modified red clay was 20.7%.