Abstract: The multiwalled carbon nanotubcs(MWNTs) was treated with strong oxidizability acid and the functional multiwalled carbon nanotubes (MWNTsCOOH) were formed. The surface functional groups of MWNTs before and after treatment were analyzed by Fourier transform infrared spectrometer (FTIR). Then ABPBO/MWNTsCOOH nano composites were successfully prepared by in situ polymerization．The results of FTIR analysis show that the surface of MWNTs after treatment contains carboxyl groups and hydroxyl groups, and the modified MWNTs can be homogeneously dispersed in the ABPBO matrix. ABPBO/MWNTsCOOH nano composites have super thermal resistance like ABPBO. The mechanical properties and optical properties are also greatly improved.