Abstract: A car starter working under very low temperature and its protection circuit, include a positive electrode output end, a negative electrode output end, an MCU single-chip microcomputer, a starter, a power heating circuit, and a MOS tube control circuit. The positive electrode is connected with the positive electrode output end and the power heating circuit. Two pins are drawn from the MCU single-chip microcomputer, connecting with one of two ends of the MOS tube control circuit. Another three pins are drawn from the MCU single-chip microcomputer, connecting with the power heating circuit. An independent power heating circuit works in very low temperature, allowing the batteries of the car starter to achieve a reasonable working temperature and solving the difficulty in starting the car in a temperature of ?40° C. The power heating circuit turns off outputs immediately when short-circuiting, solving the safety issues in using the car starter effectively.