The invention discloses a level conversion circuit and a level conversion method. The level conversion circuit comprises a current mirror, a first NMOS transistor and a second NMOS transistor, gates of the first NMOS transistor and the second NMOS transistor are connected to the same bias voltage. A drain electrode of the first NMOS tube is connected with one side of the current mirror, and the drain electrode of the second NMOS tube is connected with the other side of the current mirror. The source electrode of the first NMOS transistor is connected with an input voltage, and the source electrode of the second NMOS transistor is connected with a threshold voltage; the first NMOS transistor and the second NMOS transistor convert the input voltage and the threshold voltage into corresponding currents respectively and input the currents to the two sides of the current mirror; the current mirror compares two currents input from the first NMOS tube and the second NMOS tube, converts the two currents into corresponding voltages and outputs the voltages from the other side of the current mirror; the first input end of the hysteresis inverter is connected with voltage output by the current mirror, and the second input end is connected with power supply voltage; and when the input voltage is greater than the threshold voltage, the voltage output by the current mirror is zero, and the output voltage of the hysteresis inverter is the power supply voltage. According to the invention, the requirement on an input signal is reduced, and level conversion is realized.