We discussed the effects of MWNTs surface treatments on MWNTs/PI hybrid films in tensile strength. Used by ultrasonic，mixed acid and Fenton three methods to treat MWNTs，then through in-situ polymerization and heat imidization to prepare MWNTs/PI hybrid films. The results showed that Ultrasonic treatment just improved the dispersion of MWNTs，was not obvious to the promotion of the PI film tensile strength.MWNTs were cut short and improve the dispersion after mixed acid method. The surface of MWNTs were grafted onto the hydroxyl functional groups. And improved the interaction of two phase interface，made the tensile property of the PI films to effectively improve. MWNTs were cut short and improve the dispersion after Fenton treatment，but the wall structure of MWNTs was not damaged. The surface of MWNTs was grafted onto the hydroxyl and carboxylic acid. MWNTs with PI formed strong interaction interface. The tensile property of the PI films was Significantly improved，the largest extent was up to 13. 9%.