NOVELTY - A dried carbon nanotube and inorganic acid are mixed, diluted and washed with deionized water, filtered and vacuum dried, to obtain purified carbon nanotube. The acidified carbon fiber is obtained using purified carbon nanotube. The acidified carbon nanotube is obtained using acidified carbon fiber. The ammoniated carbon nanotube is obtained using acidified carbon nanotube. The carbon nanotube-modified carbon fiber reinforced polyimide composite material is obtained using carbon fiber grafted with carbon nanotube and amino group.    USE - Manufacture of carbon nanotube-modified carbon fiber reinforced polyimide composite material used in fields of mechanical, electronic, aerospace, wind power generation and transportation.    ADVANTAGE - The carbon nanotube-modified carbon fiber reinforced polyimide composite material is efficiently prepared with excellent strength.    DETAILED DESCRIPTION - A dried carbon nanotube (1-10 g) and inorganic acid (10-10000 ml) are added for mixing, processed for 1-24 hours with ultrasonic wave of 1-120 kHz and centrifugal speed of 10-106 rpm, heated at 20-150 degrees C, reacted for 1-48 hours, diluted and washed with deionized water and vacuum filtration is performed with microporous membrane and vacuum dried at 25-150 degrees C for 1-48 hours, to obtain purified carbon nanotube. The dried carbon nanotube (100 g) and strongly oxidizing acid (10000 ml) are mixed, processed for 0.1-12 hours, heated at 25-120 degrees C, agitated and reflux reaction is performed for 0.2-12 hours, washed with deionized water, vacuum filtration is performed with filter paper and vacuum dried at 25-200 degrees C for 1-48 hours, to obtain acidified carbon fiber. The purified carbon nanotube (1000 g) and strongly oxidizing acid (1000 ml) are mixed, processed for 0.1-80 hours, heated at 25-220 degrees C, agitated and reflux reaction is performed for 1-80 hours, diluted and washed with deionized water, vacuum filtration is performed with microporous membrane and vacuum dried at 25-200 degrees C for 1-48 hours, to obtain acidified carbon nanotube. The obtained carbon nanotube (1000 g), diamine or polyamine (1000 ml), organic solvent and condensing agent are mixed, processed for 0.1-96 hours, reacted at 25-200 degrees C for 1-96 hours, vacuum filtration is performed, washed and vacuum dried, to obtain ammoniated carbon nanotube. The obtained aminated carbon nanotube (100 g), acidified carbon fiber (1000 ml), organic solvent (1000 ml) and condensing agent (1-10 g) are mixed, reacted at 25-220 degrees C for 0.1-96 hours, diamine or polyamine and condensing agent are added and reacted for 1-96 hours, vacuum filtration is performed and vacuum dried, to obtain carbon fiber-grafted with carbon nanotube and amino group. The obtained ammoniated carbon nanotube (1-10 g) is mixed with polyimide resin, reacted at 25-220 degrees C for 0.1-24 hours, vacuum die stamping is performed with modified carbon fiber reinforced component and reacted at 50-400 degrees C for 0.5-48 hours, to obtain carbon nanotube-modified carbon fiber reinforced polyimide composite material.