The invention discloses an adjustable mechanical flocculation reaction method for enhancing coagulation by using grids, which relates to the field of water treatment and is used for solving the problem that energy cannot be uniformly distributed into water when stirring paddles are used for coagulating during the conventional water treatment. The method comprises the following steps of: I, arranging a grid in each region between a horizontal shaft and a vertical shaft on blades of a first-stage stirring paddle and a second-stage stirring paddle respectively, wherein the diameter of the mesh inscribed circle of each grid on the first-stage stirring paddle is 5-50 millimeters, the diameter of the mesh inscribed circle of each grid on the second-stage stirring paddle is 10-60 millimeters, and the diameter of the mesh inscribed circle of each grid on the second-stage stirring paddle is required to be 5-15 millimeters larger than that of the mesh inscribed circle of each grid on the first-stage stirring paddle; and II, setting the number of revolutions of the first-stage stirring paddle as 2-5 revolutions per minute, the number of revolutions of the second-stage stirring paddle as 1-3.5 revolutions per minute and the number of revolutions of the third-stage stirring paddle as 0.5-2.5 revolutions per minute. The method is applied to industries of water treatment, chemical industry and the like.