The invention relates to a method for controlling convexity of a hot-rolled aluminum plate based on a dynamic sectional cooling technique. The method comprises the following steps of (1) according to the detection cycle of a convexity instrument, determining the control cycle of dynamic sectional cooling; (2) establishing a fuzzy membership function of convexity deviation, and performing fuzzy processing on the convexity deviation in each control cycle; (3) establishing a fuzzy membership function of convexity deviation change rate, and performing the fuzzy processing on the convexity deviation change rate from the second control cycle; (4) establishing a fuzzy rule table of cooling grade change, forming four combinations by the convexity deviation fuzzy value and the convexity deviation change rate fuzzy value of each control cycle, and respectively calculating the adjusting amount of the cooling grade of each combination; (5) adopting a weighted average method to perform defuzzification on the adjusting amounts of four cooling grades; (6) correcting sectional cooling setting according to the defuzzification results. The method has the advantage that the intra-plate difference control level of the convexity of the hot-rolled aluminum plate is obviously improved.