A clock synchronization method, customer premises equipment and a clock synchronization system are provided. The customer premises equipment reads a first time stamp when receiving a first specific position of a first DMT signal sent by central office equipment; reads a second time stamp when sending a second specific position of a second DMT signal; receives a third time stamp and a fourth time stamp that are sent by the central office equipment through a data information channel. The third time stamp is read when the central office equipment sends the first specific position of the first DMT signal, and the fourth time stamp is read when the central office equipment receives the second specific position of the second DMT signal. The customer premises equipment adjusts a clock of the customer premises equipment according to the first, second, third and fourth time stamps.