The disclosure discloses a method and reagent for improving a yield of selective dispersion of semiconducting carbon nanotubes. The method comprises: fully mixing single walled carbon nanotube samples, a first polymer, and a second polymer in a solvent to form a liquid phase mixed system, enabling the single walled carbon nanotube samples to be fully dispersed in the liquid phase mixed system, centrifuging the liquid phase mixed system, and separating a supernatant to implement selective separation of the semiconducting single walled carbon nanotubes; wherein both the first polymer and the second polymer can specifically bind to the semiconducting single walled carbon nanotubes; a speed of binding the first polymer to the semiconducting single walled carbon nanotubes is greater than a speed of binding the second polymer to the semiconducting single walled carbon nanotubes; and a binding strength between the first polymer and the semiconducting single walled carbon nanotubes is less than a binding strength between the second polymer and the semiconducting single walled carbon nanotubes. The disclosure can realize high-yielding selective separation of high-purity and highly dispersive semiconductoring single walled carbon nanotubes, thereby reducing costs, and improving the repeatability and stability of the separation.