Communication method of diagnosis maintenance terminal and vehicle-mounted host and diagnosis maintenance system

The invention discloses a communication method of a diagnosis maintenance terminal and a vehicle-mounted host and a diagnosis maintenance system. According to the method, after the diagnosis maintenance terminal receives a starting command of the vehicle-mounted host, a requiring frame is sent to the vehicle-mounted host. After the vehicle-mounted host continuously receives a plurality of effective requiring frames, the communication connection is successfully established, and an idle frame containing communication connection successfully-established information is sent to the diagnosis maintenance terminal. The diagnosis maintenance terminal receives the idle frame containing the communication connection successfully-established information and the communication connection of the vehicle-mounted host is successfully established, so that the normal communication connection between the diagnosis maintenance terminal and the vehicle-mounted host is realized.