The special electrification of nano-Montmorillonite (MMT) was used to gain organic modified montmorillonite (O-MMT) with long alky side chain containing quaternary ammonium salt by ion exchange. The O-MMT obtained was used for preparing nano-composite EVA/O-MMT with melt blending method. The depressive effects of EVA/O-MMT on Changqing waxy crude oil were studied and compared with the pure EVA depressant. The crystallization characteristics of crude oil was investigated by differential scanning calorimeter (DSC) and morphology of their wax crystal with undoped/doped EVA/O-MMT analyzed using polarized light microscope. The result showed that there was the best performance when addition of EVA/O-MMT was at 50 mg·kg-1. Compared with EVA

EVA/O-MMT could make crude oil gelation point further decrease 2.5℃

did average viscosity reduce 25% at 5℃

the maximum rate of viscosity reduction could be up to 28.2%

and the yield stress of crude oil decreased up to 55.5%. DSC results showed that the addition of nano-montmorillonite could rise the initial crystallization temperature of EVA

could widen the crystallization temperature range and reduce wax precipitation point of crude oil. Microscopic results showed the addition of EVA/O-MMT made wax crystal structure of crude oil more compact.