Abstract: Structure health monitoring technology for composites is an important development direction and new monitoring methods are emerged. Carbon nanotubes(CNTs) have been widely studied because of their excellent sensors properties. This paper introduces the mechanism of piezoresistive effect of CNTs, and summarizes the piezoresistive properties of CNTs film and researches of the related applications. The paper then designs the experimental solution of the structural health monitoring(SHM) of composites using CNT polymer film sensors based on the piezoresistive effect. Sensors based on matrix-monitoring principle are pasted on surface. Signal processing methods with feature extraction and pattern recognition are used to predict, identify and locate early failure and the failure style of composites.