The invention provides a sulfur-carrying porous titanium dioxide/carbon nano composite fiber. A preparation method is characterized by comprising the following steps: preparing a polydopamine-coated titanium dioxide precursor/polystyrene composite fiber by combining an electrostatic spinning technology and an in-situ polymerization reaction bath collection method, and then carrying out high-temperature carbonization and low-temperature melting sulfur filling treatment to obtain the sulfur-loaded porous titanium dioxide/carbon nano composite fiber. The prepared porous titanium dioxide/carbon nanofiber composite material has the advantages of being stable in chemical property, good in conductivity, good in mechanical property and the like. The prepared porous titanium dioxide/carbon nanofiber composite material is controllable in morphology and has high porosity and high specific surface area. The porous titanium dioxide/carbon nanofiber composite material prepared by the invention is anideal electrode material of a lithium-sulfur battery, and can improve the conductivity of a sulfur positive electrode, increase the loading capacity of sulfur, buffer the volume change, effectively inhibit the shuttle effect, and remarkably improve the rate and cycle performance of the lithium-sulfur battery.