The invention provides an automobile speed determining method and device, and an automobile, and relates to the technical field of automobile control. The automobile speed determining method comprisesthe steps that the rotational speed of a motor of the automobile and the rotational speeds of a plurality of wheels are obtained in real time; if the current obtained rotational speeds of the multiple wheels are all within a first preset range, the first theoretical automobile speed is calculated according to the rotational speeds of the multiple wheels; if the current obtained rotational speed of the motor is within a second preset range, the second theoretical automobile speed is calculated according to the rotational speed of the motor; and the current output automobile speed of the automobile is determined according to the first theoretical automobile speed and the second theoretical automobile speed. According to the automobile speed determining method and device, and the automobile,the calculated theoretical automobile speeds are subjected to security checking, the possibility of accident occurring caused by automobile speed miscalculation due to unit exception is decreased, and the safety and reliability of the automobile are improved.