Abstract: In this paper carbon nanotubes (CNTs) were separately treated with dense HCl, dense HNO₃，bromic acid, HNO₃，H₂SO_4-HNO3 and K₂Cr₂O₇-H₂SO₄, in order to increase the reactionof CNTs/BMI/BA svstemand interfacial interaction between resin and CNTs. XRD and TEM were used to characterize the structure of carbon nanotubes. The influence of CNTs/BMI/BA on the reaction characteristics was studied using DSC and mechanical properties of the composites were also investigated with CNTs treated by different acids. It was found that the CNTs treated with mixture of HNO₃-H₂SO₄(4^#CNT) enhanced the reaction of BMI/BA/CNTs system and greatly improved the mechanica properties of bismaleimide resins.When the contents of 4^# CNT in the BMI/BA resin were 1 wt % anc2wt %，the impact strength increased by 16.92 % and 23.06 %, the flexural strength increased by 7.61 % and 6.47 %，respectively, based on those containing neat CNTs.

Key words: carbon nanotube, bismaleimide, purification, reaction activity, mechanical property