Pores in aggregated multi-walled carbon nanotubes (MWNTs) can be mainly divided into inner hollow cavities of smaller diameter (narrowly distributed, mainly 3.0-4.0 nm) and aggregated pores (widely distributed, 20-40 nn), formed by the interaction of isolated MWNTs. The two types of pores shall, respectively, determine nitrogen cryogenic capillarity process under different pressures. It is worth to note that ultra-strong nitrogen capillarity in the aggregated pores (590 mg N-2/g) contributes to the 78.5% of the total adsorption amount (up to 750 mg/g near to the ambient pressure), showing that the aggregated pores of the MWNTs are much more important than their inner cavities for adsorption and capillarity in some cases.