The invention discloses a method for improving the surface activity of aramid fiber. The method comprises the following steps of: (1) immersing the aramid fiber in acetone, heating and boiling for 1 hour, further immersing into anhydrous ethanol, and heating and boiling for 1 hour; and then placing into deionized water for washing, and drying for 2 hours after the treatment; and (2) performing surface activation treatment on the aramid fiber: (a) preparing a hydrogen peroxide solution with the concentration of 20%-60%; (b) cutting the aramid fiber after pretreatment into samples of 20cm, and placing into the hydrogen peroxide solution for performing treatment at the temperature of 0 DEG C-80 DEG C for 30min-90min; (c) washing with the deionized water till the pH value of a washing solution is 7; and (d) drying after washing to obtain the aramid fiber with surface modification. The treatment method disclosed by the invention is simple, the interfacial binding strength of an aramid fiber-reinforced composite material can be greatly improved, the mechanical strength of the aramid fiber can be also kept unchanged, the equipment is simple, the operation is convenient, and the industrial continuous treatment is convenient to realize.