The embodiments are an aircraft time synchronization system and method. The system comprises: a first communication module and a second communication module, wherein data transmission is performed between the first communication module and the second communication module via a communication line, and an I/O interface of the first communication module is connected to the I/O interface of the second communication module via an interruption signal line; the first communication module sends the data information to the second communication module via the communication line, and at the same time sends the triggered interruption signal to the second communication module via the interruption signal line; the second communication module performs time synchronization with the first communication module based on the communication time difference and system time difference with the first communication module determined according to the receiving time of the data information and interruption signal and the sending time.