The invention discloses a method for controlling head and tail size amplifying rates dynamically based on different width expansion ratios. Different head and tail size amplifying lengths are determined according to the different width expansion ratios of rolled steel plates. The method comprises the steps specifically as follows: materials with different section widths are divided into four grades, namely, grade A: 1660, grade B: 1860, grade C: 2060, and grade D, 2260; according to the section widths of different grades, the size amplifying rates are selected dynamically, wherein for the grade A, 1660, the size amplifying length is 1-1.1; the grade B, 1860, the size amplifying length is 1.1-1.2; the grade C, 2060, the size amplifying length is 1.2-1.45; and the grade D, 2260, the size amplifying length is 1.45-3. According to the method, the size amplifying lengths can be controlled dynamically according to the different width expansion ratios of the rolled steel plates, and the yield is increased.