In this study, multi-wall carbon nanotube (MWCNT) supported Co-Mo nanocatalysts with changes in synthesis steps, one and two-step, were prepared through impregnation to be used in extra heavy oil hydrocracking process. In both of the synthesized nanocatalysts, the Co/Mo weight ratio was 1/3. The nanocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and accelerated surface area and porosimetry (ASAP) methods. The results showed that the nanocatalysts prepared through a two-step impregnation method had higher surface area and pore volume than the other synthesized nanocatalysts. The nanocatalysts were used in hydrocracking process under mild operating conditions, 260-300 ℃ and at H2 initial pressure of 5 MPa. Hydrocracking of extra heavy oil was conducted in an autoclave reactor. The results indicated that both nanocatalysts were capable of hydrocracking heavy oil at mild operating conditions. However, the nanocatalysts synthesized through the two-step impregnation exhibited higher performance, better heavy oil to light oil conversion, and better sulfur removal than the other methods. This superiority is due to the nanocatalyst’s structure and better distribution of metal clusters on the support.