The invention discloses a preparation method of nano-carbon fiber with high specific surface area. The method uses the resol resin with low molecular weight as a carbon precursor, uses the polymer with high molecular weight as a spinning auxiliary agent, and obtains a spinning dope by adding organic matter containing silicon into a stock solution. The as-spun fibre having nanoscale is prepared by electrospinning technique, and the porous nano-carbon fibre having high specific surface area is prepared by the processes such as solidification, carbonization, and acid pickling. The method can adjust and control the specific surface area of the nano-carbon fibre by controlling the addition of the pore forming agent, and has advantages such as simple technology and strong operability.