The invention relates to a method for centrifugal separation of carbon nanotubes with a density gradient method. The method comprises the following steps: ultrasonically dispersing carbon nanotubes in an aqueous solution; preparing sucrose solutions with respective concentrations of 5%, 10%, 15%, 20% and 25%, according to mass percentage; sequentially and slowly adding a certain amount of sucrosesolution into a same centrifuge tube to preparing a gradient solution; slowly dropping the ultrasonically dispersed carbon nanotube solution on the surface of the gradient solution, centrifuging witha horizontal rotor at 4,000rpm for 60min, and slowly sucking out the centrifuged mixed solution in equal two parts according to the percentages of solutions composing the gradient solution; and obtaining carbon nanotubes with different lengths. The inventive method has the advantage of simple process, can obtain carbon nanotubes with uniform length, and can be applied in the field of drug carriers.