In order to ensure the normal use of steel-concrete composite structures and effectively monitor the slip damage of PBL shear key, a method for monitoring the slip damage of PBL shear key in steel-concrete composite structures based on piezoelectric ceramics was proposed. Two groups of specimens of PBL shear key were designed to monitor slip damage in steel-concrete composite structures. One group of specimen was coated with a layer of butter at the interface between steel and concrete, while the other group was not coated with butter. The piezoelectric intelligent aggregate actuators and piezoelectric ceramic sensors were arranged in the specimens to collect response signals of slip damage. The study results show that the amplitude of the signal received by the sensors decreases with the increase of slip damage degree, and the energy of the wavelet packet decreases with the increase of relative slip amount. The butter makes the interface between concrete and steel closer and reduces the dissipation of stress wave in the propagating process.