AES is the most used block cipher, and its round-reduced variants are popular underlying components to design cryptographic schemes. How to effectively distinguish round-reduced AES from random permutations has always been a hot research topic. Currently, the longest rounds of AES can be distinguished is 6 rounds, where the best result is the 6-round exchange distinguisher with the data complexity \(2^{84}\) . In this paper, we extend the classical boomerang distinguisher which uses only one boomerang property to use two or more related boomerangs and the technique of ‘friend pairs’ to enhance the distinguishing effect. We propose the frameworks of the re-boomerang and boomerang chain distinguishers and apply them to 6-round AES. The re-boomerang distinguisher uses two related boomerangs sequentially, which have the same upper truncated differential trail in the forward direction. A plaintext pair is called a right pair if it follows this truncated differential trail. By the first boomerang, a target set of plaintext pairs containing one right pair can be obtained. Then for each pair in the target set, construct its ‘friend pairs’ as the input of the second boomerang to distinguish the cipher. Due to the dependence of the two boomerangs, all ‘friend pairs’ of the right pair are right pairs, so the probability of the second boomerang is increased. To further improve the complexity, we insert a new boomerang in the middle of the re-boomerang and repeat it to reduce the target set. Combining the strategies of using more data in each boomerang and repeating the distinguishing process several times, we give a boomerang chain distinguisher on 6-round AES with success probability \(60\%\) and complexity \(2^{76.57}\) , reduced by a factor of 172 compared with the previous best result. This is a new record for the secret-key distinguisher on 6-round AES.