Perovskite-type La_0.9K_0.1CoO_3−δ nanofibers were fabricated successfully using an electrospinning technique with calcination, based on the successful preparation of LaCoO₃ nanofibers considering the enhancement in the activity by K⁺, which could facilitate oxygen species transfer and accelerate redox circulation. Furthermore, a hollow structure could provide more pathways for soot transportation and transmission of reaction gas (O₂ and NO), improving the contact efficiency of soot–catalyst–gas and contributing to the enhancement in catalytic activity. However, the grain size increasing in the calcination has a great influence on the formation of the hollow structure. Thence, the introduction of some Sr²⁺ in La_0.9K_0.1CoO_3−δ nanofibers was taken into consideration to construct the hollow structure, by the inhibition of grain growth during heat treatment at a high temperature. Meanwhile, the Sr²⁺ doping could further promote the catalytic activity. After comparison, an appropriate amount of Sr²⁺ was introduced and the perovskite-type La_0.63Sr_0.27K_0.1CoO_3−δ nanotubes were successfully prepared in this work as a result. Besides, some related catalysts were also prepared for comparison with the same method. These as-prepared catalysts were investigated by a series of characterization techniques. The activity evaluation of the catalysts was carried out through temperature programmed oxidation in 5% O₂ and 2000 ppm NO, as well as in the presence of 6% H₂O. According to the activity data, La_0.63Sr_0.27K_0.1CoO_3−δ nanotubes could be recognized as a high-performance catalyst for soot oxidation.