The evolution of multi-walled carbon nanotubes (MWCNTs) under hydrothermal condition was investigated, because the hydrothermal method (HTM) has been utilised for commercial production of advanced engineering materials To synthesise MWCNTs by hydrothermal process using mixed aqueous solution diethylenetriamine, polyethyleneglycol (PEG) and NaOH were used as starting materials We investigated the effect of hydrothermal temperature, time, and amount of formative compounds Hydrothermal reaction temperature was in the range from 150 to 180 degrees C The aim of the present work is to presentation hydrothermal synthesis as a new processing method for fabrication of MWCNTs, without the addition of metal catalyst The homogeneity of hydrothermal processes, cheapness, and availability of amorphous carbon materials, without the need of catalyst, are advantages favouring the scaling-up of the new method The treatment of higher volumes would only require autoclaves with increasing load-bearing capacity Synthesised MWCNTs were analysed with a scanning electron microscope (SEM), a high resolution transmission electron microscope (HRTEM), thermo-gravimetric analysis (TGA), and Raman spectroscopy This result also presented a controllable way to synthesise MWCNTs with high purity Indeed, present work will introduce new chapter in synthesising MWCNTs for scientific and engineering