Embodiments of this application disclose a motor vehicle self-driving method and a terminal device. The method includes: obtaining, by a terminal device, vehicle external-environment data of a position of a motor vehicle and initial positioning precision of the motor vehicle; determining, by the terminal device, a target driving parameter of the motor vehicle based on the vehicle external-environment data and the initial positioning precision; and controlling, by the terminal device, the motor vehicle to drive based on the target driving parameter. In the embodiments of this application, the terminal device determines the target driving parameter of the motor vehicle based on the vehicle external-environment data and the initial positioning precision. In this way, the target driving parameter varies with the vehicle external-environment data, and further matches an external environment, thereby improving self-driving safety of the motor vehicle.