Carbon nanotubes-alumina (CNTs-Al2O3) composite ceramics with 25vol% CNTs were fabricated by sol-gel method and followed by hot-pressing. The resultant ceramics and powders were characterized for their microstructure and composition by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and infrared spectra (IR). The mechanical properties of the ceramics were measured by micromechanical testing system (MTS). The results show that both ultrasonic calefaction process during the gelation of alumina sol and annealing process during the sintering can remarkably enhance the fracture toughness and flexural strength of CNTs-Al2O3 composite ceramics, compared with the composite ceramics without undergoing these processes. It is believed to be due to the relatively uniform dispersion of CNTs and the lower thermal stress in the matrices.