This work describes the potential capability of ultrafine porous carbon fibers (UPCF) prepared via electrospinning in the removal of SO2 from a mixture gas stream. A series of conventional PCF (CPCF) and ultrafine PCF (UPCF) were produced under the identical conditions and UPCF was also modified. Compared to the CPCF, experimental results showed that the UPCF had a better adsorption capacity for SO2 due to its higher surface area and microporous volume. After the modification of the UPCF, adsorption capacities of UPCF for SO2 were improved further via increasing the N-containing amount of UPCF and substrate which was followed by few changes in its specific surface area. The optimum concentration of modified reagent is 10%. From the results of the fatigue test, it has been found that both the UPCF and the modified UPCF showed a good durability.