The invention relates to an automobile insulation resistance detection circuit and method, and the circuit comprises a negative bleeder resistor, a positive bleeder resistor, a first sampling resistor, a second sampling resistor, a third sampling resistor, a fourth sampling resistor, a fifth sampling resistor, a sixth sampling resistor, a negative switch, and a positive switch. One end of the negative bleeder resistor is connected with the negative electrode of a detected battery, and the other end of the negative bleeder resistor is grounded. One end of the positive bleeder resistor is connected with the positive electrode of the detected battery, and the other end is grounded. One end of the first sampling resistor is connected with the negative electrode, and the other end of the sampling resistor is connected with one end of the negative switch. The other end of the negative switch is connected with one end of the second sampling resistor, and the other end of the second sampling resistor is grounded. One end of the third sampling resistor is connected with the positive electrode, and the other end of the third sampling resistor is connected with one end of the positive switch. The other end of the positive switch is connected with one end of the fourth sampling resistor, and the other end of the fourth sampling resistor is grounded. One end of the fifth sampling resistor is connected with the positive electrode, and the other end of the fifth sampling resistor is connected with one end of the sixth sampling resistor. The other end of the sixth sampling resistor is connected with the negative electrode. According to the scheme of the invention, the circuit can improve the detection precision of insulation resistance.