Abstract: The three different kinds of nano montmorillonites (nMMT) (Na-montmorillonite(Na-MMT), nMMT modified by amino acid(OMMT-A), and nMMT modified by CH₃(CH₂)₁₇N(CH₃)[(CH₂CH₂OH)₂]⁺(OMMT-B)) were added into the polyamide 6-66 (PA6-66) matrix through melt blending to prepare different nano montmorillonite/polyamide 6-66 (nMMT/PA6-66) composites. The effects of different surface modified nMMTs on crystallization behaviors, rheology properties and mechanical properties of PA6-66 were investigated. It is observed that nMMTs can promote the formation of γ-crystal and increase the crystallization temperature of nMMT/PA6-66 composites, but the efficiency of heterogeneous nucleation of OMMT-B decreases to a certain extent. Simultaneously, OMMT-B has better ability to improve the storage modulus and flow ability of PA6-66 compared with other two nMMTs. The mechanical properties results show that nMMTs can increase the strength and decrease the toughness of PA6-66, but the effects are different. Among these composites, the nMMT/PA6-66 composite incorporated with OMMT-B has the best mechanical performance, not only the tensile strength and the flexural strength are raise 26% and 28% compare with the pure PA6-66, respectively; but also the toughness is close to unchanged. Based on the comprehensive results, the effects of different surface modified nMMTs on the properties of PA6-66 have been studied systemic, which is mainly depends on the interaction between the organic modifier of nMMT and PA6-66 molecular chains.