The invention relates to a band-gap reference voltage circuit comprising a first bipolar transistor, a second bipolar transistor, a first resistor, a second resistor, a third resistor and a fourth resistor. The base electrode and the collector electrode of the first bipolar transistor are grounded, and the emitter electrode of the first bipolar transistor is grounded through the first resistor. The base electrode and the collector electrode of the second bipolar transistor are grounded, the emitter electrode of the second bipolar transistor is connected to one end of the third resistor, and the other end of the third resistor is grounded through the second resistor; one end of the fourth resistor is grounded, and a current in direct proportion to a mixed current of a current flowing through the third resistor and a current flowing through the second resistor flows through the fourth resistor, so that the other end of the fourth resistor obtains a reference voltage. The fourth resistor comprises a plurality of adjustable resistor units with each connected in parallel with a corresponding switch, and the resistance value of the fourth resistor is adjusted through controlling the switching on/off of each switch, furthermore, the reference voltage can be adjusted to obtain a reference voltage with higher precision.