The invention discloses a device for the safety of a car. The device comprises an RF (Radio Frequency) antenna, an RFID (Radio Frequency Identifier) module, a GSM (Global System for Mobile Communications) unit, a data processing unit, a control unit and a car circuit; a signal of the RFID module is received by the antenna and then sent to the data processing unit; then the signal is converted into a digital signal which is immediately sent to the control unit; and the control unit is used for obtaining identification data and comparing the identification data with stored information. If the identification data is in accordant with the stored information, the control unit is used for sending a control signal to ensure that a first relay and a second relay are actuated after a theft-proof state is released so that the car can be normally started up. If the identification data is not in accordant with the stored information, the circuit is locked and an alarm is sent to the owner of the car via a short message so that the safety of the car can be ensured.