A diagnostic method for a vehicle in a diagnostic system, the method comprising the following steps performed by a management server: receiving a connection request message sent by a terminal, wherein the connection request message is used for requesting address information of a diagnostic server corresponding to a to-be-diagnosed vehicle (201, 202); determining the corresponding diagnostic server according to the connection request message; sending the address information of the diagnostic server to the terminal; and wherein the method further comprises: establishing, by the terminal, a communication connection with the diagnostic server according to the address information; characterized in that the method further comprises: receiving, by the management server, an expert assistance request message sent by the terminal; sending, by the management server, a request assistance signal to a background device according to the expert assistance request message, the request assistance signal being used to request the background device to control the diagnostic server; and controlling, by the background device, the diagnostic server to perform data interaction with the terminal by a user of the background device. receiving a connection request message sent by a terminal, wherein the connection request message is used for requesting address information of a diagnostic server corresponding to a to-be-diagnosed vehicle (201, 202); determining the corresponding diagnostic server according to the connection request message; sending the address information of the diagnostic server to the terminal; and wherein the method further comprises: establishing, by the terminal, a communication connection with the diagnostic server according to the address information; characterized in that the method further comprises: receiving, by the management server, an expert assistance request message sent by the terminal; sending, by the management server, a request assistance signal to a background device according to the expert assistance request message, the request assistance signal being used to request the background device to control the diagnostic server; and controlling, by the background device, the diagnostic server to perform data interaction with the terminal by a user of the background device. establishing, by the terminal, a communication connection with the diagnostic server according to the address information; characterized in that the method further comprises: receiving, by the management server, an expert assistance request message sent by the terminal; sending, by the management server, a request assistance signal to a background device according to the expert assistance request message, the request assistance signal being used to request the background device to control the diagnostic server; and controlling, by the background device, the diagnostic server to perform data interaction with the terminal by a user of the background device. receiving, by the management server, an expert assistance request message sent by the terminal; sending, by the management server, a request assistance signal to a background device according to the expert assistance request message, the request assistance signal being used to request the background device to control the diagnostic server; and controlling, by the background device, the diagnostic server to perform data interaction with the terminal by a user of the background device.