In order to monitor the health condition of composite tail structure under load condition,a structural health monitoring (SHM) method based on the ultrasonic guided waves and canonical correlation analysis was proposed in this paper.First,the correlation coefficient between the reference signal representing the structural health condition and the damage signal is defined as the damage index.The threshold of damage index was determined based on a typical structure loading test.Then,the numbers of paths which damage indices exceed the threshold were chosen as the indicator of structure health status.Finally,the effectiveness of the proposed method for monitoring the structural damage expansion of the composite aircraft is verified by the SHM experiment of a fullscale composite horizontal tail.The experimental results show that the change of structural damage index can reflect the trend of structural health status,and the inservice structural health monitoring method can realize realtime monitoring of composite structure.