The invention discloses a recorder for automobile running parameters and a calculating method of the automobile running parameters. The recorder comprises a power supply module, a singlechip microcomputer module, an inertial navigation module, a communication module, a switching value signal processing circuit and a storage module, wherein the inertial navigation module, is connected with the singlechip microcomputer module; the communication module is connected between the singlechip microcomputer module and an on-board diagnosis system OBD interface of an automobile; the switching value signal processing circuit is connected between the singlechip microcomputer module and an automobile lamp and brake pedal signal bundle; the storage module is connected with the singlechip microcomputer module. The calculating method comprises the following steps: acquiring the longitudinal speed and the integral heading angle speed from the OBD interface and the inertial navigation module by the singlechip microcomputer module; and calculating the turning radius, the wheel steering angle and the steering wheel angle of the automobile according to a formula. The recorder has the beneficial effects that an automobile body is little in modification, and no sensors are additionally installed on the automobile, so that the installation cost is low; the recorder is simple in structure, small in size and convenient to popularize; the recorder can be used for recovering the state of the automobile, operation of a driver and the long-term driving behavior of the driver before accidents so as to provide an accurate basis for responsibility analysis of the traffic accidents.