Preparation method of high-strength carbon fiber

The invention provides a preparation method of a high-strength carbon fiber, which is characterized by comprising the following specific steps: firstly, mixing 0.01-2 portions by weight of carbon nano tubes and 100 portions by weight of solvent and carrying out ultrasound treatment for 1.5 to 3 hours at the power of 300w to 600w by an ultrasonic cell disruptor; secondly, adding 0.01-5 portions byweight of polymeric plasticizer in the obtained mixing solution and carrying out ultrasound treatment for 1 to 2 hours at the power of 300w to 600w by an ultrasonic cell disruptor; and thirdly: forming a coating with the thickness of 100 nm to 300 nm on a pre-oxidized fiber for spinning by using the mixed solution in the second step and obtaining the high-strength carbon fiber by carbonization. The preparation method can ensure that the tensile strength of the carbon fiber is improved by 15-30 percent and the toughness of the carbon fiber is improved by 30 percent.