A handover method for a mobile terminal, comprising: a mobile terminal sending a data frame to a second access point when the MT needs to hand over from a cell covered by a first wireless AP service to a cell covered by a second AP service, with the data frame containing an associated number between the MT and the first AP and a media access control address of the first AP; wherein the second AP stores mobile terminal certification and association information about a cell which overlaps with a cell covered by the second AP service, including the mobile terminal certification and association information about a cell covered by the first AP service; and the second AP stores a shared key of an AP of a cell which overlaps with a cell covered by the second AP service, including the shared key of the first AP; after having received the data frame, the second AP comparing the associated number between the MT and the first AP and the MAC address of the first AP in the data frame with corresponding contents in mobile terminal certification and association information stored by the second AP, when the comparison result presents to be consistent, the second AP encrypting a new key using the shared key of the first AP and sending the encrypted new key to the MT, and the MT relieving the association with the first AP and obtaining an associated number between the MT and the second AP; and the MT adding an association with the second AP according to the obtained associated number between the MT and the second AP, decrypting the obtained new key, and carrying out a data transmission with the second AP using the new key. a mobile terminal sending a data frame to a second access point when the MT needs to hand over from a cell covered by a first wireless AP service to a cell covered by a second AP service, with the data frame containing an associated number between the MT and the first AP and a media access control address of the first AP; wherein the second AP stores mobile terminal certification and association information about a cell which overlaps with a cell covered by the second AP service, including the mobile terminal certification and association information about a cell covered by the first AP service; and the second AP stores a shared key of an AP of a cell which overlaps with a cell covered by the second AP service, including the shared key of the first AP; after having received the data frame, the second AP comparing the associated number between the MT and the first AP and the MAC address of the first AP in the data frame with corresponding contents in mobile terminal certification and association information stored by the second AP, when the comparison result presents to be consistent, the second AP encrypting a new key using the shared key of the first AP and sending the encrypted new key to the MT, and the MT relieving the association with the first AP and obtaining an associated number between the MT and the second AP; and the MT adding an association with the second AP according to the obtained associated number between the MT and the second AP, decrypting the obtained new key, and carrying out a data transmission with the second AP using the new key.