A CVD preparation method for minimizing camera module dot defects includes: performing ultrasonic cleaning and drying on a base substrate to obtain a pre-treated base substrate; placing the pre-treated base substrate into a reaction chamber, evacuating, and introducing nitrogen or inert gas to slightly positive pressure; simultaneously introducing precursor I and precursor II at a temperature of 500-700° C. to deposit a low-refractive-index L layer on the base substrate; halting introduction of the precursor I and the precursor II, and purging the reaction chamber with nitrogen or the inert gas; introducing raw gas precursor III and precursor IV at a temperature of 600-800° C. to deposit a high-refractive-index H layer on the low-refractive-index L layer; and halting introduction of the precursor III and precursor IV, and purging the reaction chamber with nitrogen or inert gas; and cooling to room temperature to obtain an optical element with coating films having different refractive indices.