Carbon nanotubes (CNTs) with their high mechanical, electrical, thermal and chemical properties are regarded as promising materials for many different potential applications. Chemical vapor deposition (CVD) is a common method for CNT synthesis especially for mass production. There are important parameters (synthesis temperature, catalyst and calcination conditions, substrate, carbon source, synthesis time, H-2 reduction, etc.) affecting the structure, morphology and the amount of the CNT synthesis. In this study, CNTs were synthesized by CVD of acetylene (C2H2) on magnesium oxide (MgO) powder substrate impregnated by iron nitrate (Fe (NO3)(3)center dot 9H(2)O) solution. The synthesis conditions were as follows: at catalyst calcination temperatures of 400 and 550 degrees C, calcination time of 0, 15, 30 and 45 min, hydrogen concentrations of 0, 50 and 100 % vol, synthesis temperature of 800 degrees C and synthesis time of 30 minutes. The synthesized materials were characterized by thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), X ray diffraction (XRD) and Raman spectroscopy. Effects of H-2 reduction on catalyst calcination and CNT synthesis were investigated.