The invention provides a method for electrochemically modifying surface of ultrasonic-enhanced carbon 
fiber. The method comprises the following steps of: firstly, pretreating the surface of the carbon 
fiber material, secondarily, soaking the pretreated carbon 
fiber material into an electrolytic bath filled with 
strong electrolyte solution; and by taking the carbon fiber material as an electrochemically oxidized 
anode and 
graphite as an electrochemically oxidized 
cathode, guiding in current through control of a 
voltage-stabilizing power supply, wherein the current intensity is 1A / g-2A / g; and under the conditions of ultrasonic power of 200W-2000W, ultrasonic frequency of 20kHz-100kHz, and water bath temperature of 20 DEG C-70 DEG C, carrying out 
ultrasonic oscillation for three minutes to 15 minutes to produce 
surface modification, and finally washing and 
drying to obtain surface-
modified carbon fiber. With the method, the 
surface roughness of the carbon fiber can be increased, the 
wetting property of the carbon fiber can also be improved due to introduction of polar group into the surface of the fiber, the binding property between the carbon fiber and a 
resin matrix can be enhanced, and the interface property of binding the carbon fiber with other materials can be increased.