A user information synchronization method performed by a terminal device, the method comprising: parsing and analyzing, by the terminal device, a Hypertext Transport Protocol, HTTP, request packet flowing through the terminal device to acquire domain name information of a website accessed by a user and detect whether Cookie information is included in the HTTP request packet when a webpage is accessed, and storing the Cookie information into the terminal device when the Cookie information is detected; characterised by, when it is detected that the user accesses the webpage again, if no Cookie information is included in a header of an HTTP request packet, searching, by the terminal device, in accordance with an MAC address and URL information in the HTTP request packet, for previously stored relevant Cookie information, when previously stored relevant Cookie information is found modifying the HTTP request packet by adding the previously stored relevant Cookie information to the header of the HTTP request packet, and then sending the modified HTTP request packet, so as to implement synchronization of the Cookie information of the user, wherein the step of parsing and analyzing by the terminal device an HTTP request packet flowing through the terminal device comprises: when a header of the HTTP request packet includes the Cookie information, acquiring a Media Access Control, MAC, address and the Cookie information in the HTTP request packet, and acquiring information of GET and HOST attributes in the HTTP request packet to form complete Uniform Resource Locator, URL, information, and storing the acquired information into an Encrypting File System, EFS, of the terminal device by using a preset data structure and an encryption algorithm, wherein, when no previously stored relevant Cookie information is found in the searching step, the terminal device forwarding the HTTP request packet without modification. parsing and analyzing, by the terminal device, a Hypertext Transport Protocol, HTTP, request packet flowing through the terminal device to acquire domain name information of a website accessed by a user and detect whether Cookie information is included in the HTTP request packet when a webpage is accessed, and storing the Cookie information into the terminal device when the Cookie information is detected; characterised by, when it is detected that the user accesses the webpage again, if no Cookie information is included in a header of an HTTP request packet, searching, by the terminal device, in accordance with an MAC address and URL information in the HTTP request packet, for previously stored relevant Cookie information, when previously stored relevant Cookie information is found modifying the HTTP request packet by adding the previously stored relevant Cookie information to the header of the HTTP request packet, and then sending the modified HTTP request packet, so as to implement synchronization of the Cookie information of the user, wherein the step of parsing and analyzing by the terminal device an HTTP request packet flowing through the terminal device comprises: when a header of the HTTP request packet includes the Cookie information, acquiring a Media Access Control, MAC, address and the Cookie information in the HTTP request packet, and acquiring information of GET and HOST attributes in the HTTP request packet to form complete Uniform Resource Locator, URL, information, and storing the acquired information into an Encrypting File System, EFS, of the terminal device by using a preset data structure and an encryption algorithm, wherein, when no previously stored relevant Cookie information is found in the searching step, the terminal device forwarding the HTTP request packet without modification.