Dispersions of multi-walled carbon nanotubes (MW-CNTs) assisted by non-covalent surface modification and covalent surface modification were prepared using different concentration of gallic acid aqueous solution. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the dispersion states and effect of MWNTs. FTIR results demonstrate that concentration of gallic acid has great effect on the surface modification of multi-walled carbon nanotubes. With the content of gallic acid increasing, modification effect were firstly increased and then decreased in that the optimal concentration is about 10 μg/ml as it is its solubility in water. SEM and TEM results also show that gallic acid not only can ensure the integrity of the MW-CNTs, but also can purify it. These results confirmed achievement of a good dispersion state and effect of MW-CNTs with gallic acid. The dispersion mechanism of non-covalent surface modification and covalent surface modification was analyzed.