The invention relates to a preparation method of a 
polyacrylonitrile carbon 
fiber with an evenly distributed copolymerization sequence. The preparation method comprises the following steps: determining the number of serially connected reactors; determining the ratio of fed materials of different areas in the third co-
monomer zone; carrying out 
precipitation polymerization by taking water as the medium, 
drying so as to obtain 
polyacrylonitrile powder; dissolving the 
polyacrylonitrile powder to prepare a 
spinning solution, removing the bubbles from the solution, filtering, spraying, and curing to form primary fibers, washing and subjecting the primary fibers to a 
post treatment so as to obtain polyacrylonitrile-based carbon precursor fibers; and finally subjecting the precursor fibers to pre-oxidation, 
carbonation, and a 
post treatment so as to obtain the high performance carbon 
fiber. The preparation method adopts multi-grade serially-connected stirred tank 
polymerization reactors, and raw materials are supplemented in the third co-
monomer zone according to a certain ratio in different areas so as to obtain a PAN 
copolymer with evenly distributed copolymerization sequence. Because the 
distribution uniformity of the copolymerization sequence of polyacrylonitrile precursor fibers is high, the possibility that fibers with a shell-core structure appear during the pre-
oxidation process is small. Moreover, the 
diffusion of 
oxygen gas in the radical direction of fibers is also promoted, thus the pre-oxidation reactions can be stably carried out and the heat dissipation can be controlled so as to obtain carbon 
fiber with an excellent performance.