Vehicle fault diagnosis method and system and OBD diagnosis device

The invention discloses a vehicle fault diagnosis method and system and an OBD diagnosis device. The vehicle fault diagnosis system comprises an OBD diagnosis connector and a display screen. The method comprises the steps that a user-triggered diagnosis instruction is received; according to the diagnosis instruction, the OBD diagnosis connector is controlled to carry out fault diagnosis on a vehicle connected with the OBD diagnosis connector to acquire diagnosis data; and the diagnosis data are displayed through the display screen. According to the invention, the display screen is added on the OBD diagnosis connector of the vehicle fault diagnosis system, and the diagnosis data can be displayed directly through the display screen after the OBD diagnosis connector carries out fault diagnosis on the vehicle connected with the OBD diagnosis connector; a user can directly view the diagnosis data through the OBD connector screen, which reduces the middle operation of a mobile phone or a diagnosis panel; and the user can conveniently and fast view the data.