The invention discloses a VPN protocol for a mobile device. According to the VPN protocol, a VPN client classifies intelligent terminal traffic through a traffic classifier, so that the intelligent terminal traffic can be divided into text data and non-text data; strong encryption and compression are performed on the text data, and then, encrypted and compressed data are encapsulated to a VPN tunnel; weak encryption is performed on the non-text data, and encrypted data are encapsulated to the VPN tunnel; and the above process is completed at an middleware layer. With the VPN protocol of the invention adopted, reliable encryption and transmission services can be ensured, and at the same time, the service quality of VPN services and the performance of the VPN client can be ensured.