A temperature sensor includes a NAND gate and a plurality of delay units. The NAND gate includes a first and a second input terminals, and an output terminal. The first input terminal is configured to receive an external starting control signal. The plurality of delay units are connected in series. An input end of the first delay unit is connected to the output terminal of the NAND gate. An output end of the last delay unit is connected to the second input terminal of the NAND gate, thereby forming a ring oscillator structure. The temperature sensor can realize conversion of temperature-leakage-frequency based on the ring oscillator structure in a temperature range of −40˜125° C., thereby simplifying design complexity and achieves high accuracy.