Aligned carbon nanotube (ACNT)/MnO2 nanocomposites were fabricated using the reduction between potassium permanganate and ACNT under the microwave irradiation. Due to good contact between ACNT and current collector during the charge/discharge process, compressible ACNT/MnO2 nanocomposites show better electrochemical properties compared to pure MnO2 and ACNT, such as high specific capacitance, good rate performance and cycling stability (2.7% loss of the initial value after 3000 cycles). These results demonstrate that ACNT/MnO2 nanocomposites have potential application for supercapacitors as high-rate electrode materials.