The application of concrete-encased concrete-filled steel tube (CE- CFST) structures is taking the development of arch bridge to new heights. Interfacial bonding failure between the concrete-filled steel tube (CFST) and the outer concrete would degrade the integrity and bearing capacity of the CE- CFST structures. Aiming at the hidden and random nature of interfacial damage, this paper proposes an acoustic emission-based real-time monitoring method for the interfacial damage process of CE-CFST. Three sets of CE-CFST column specimens were carried out on the push-out testing. The effect of the type of built-in steel tube on the interface bonding failure mechanism between CFST and outer concrete was discussed. The variation rule of acoustic emission characteristic parameters during the bonding failure process was analyzed. The results shown that the energy and cumulative energy of acoustic emission can well reveal the interfacial damage evolution process of CE-CFST. According to the acoustic emission energy parameters, the bonding damage process of CE- CFST columns with built-in circular steel tube can be divided into adhesive stage, local slip stage and slip stage; the bonding process of CE-CFST columns of square steel tube is divided into four stages: adhesive stage, local slip stage, friction stage and slip stage.