The invention discloses an automatic focusing method based on an improved hill climbing method, belonging to the technical field of camera focusing. The automatic focusing method comprises the following steps: 1) initialization of an algorithm, obtaining an initial sharpness evaluation value and average gray level through calculation; 2) evaluating a target image sharpness evaluation and an average gray level value in the current frame, and comparing with the previous frame; 3) performing focusing through improved hill climbing method; 4) performing parabola fitting through focusing data of the last three times of the improved hill climbing method, obtaining a horizontal ordinate of a maximum value point as the needed focusing point through calculation; 5) repeating the steps 2)-4) for thesame target, thereby realizing continuous automatic focusing for the same target. The improved hill climbing method provided by the invention has high anti-noise property, meanwhile, times of focusing is reduced greatly, and algorithm speed is improved. Further, in combination with a curve fitting method, small-step fine focusing of the existing hill climbing method is substituted, calculation amount is reduced, and fast focusing is realized.