The invention relates to a sampling circuit which is used in three level PFC circuit and voltage sampling method, aiming at solve the problem that high frequency noise of capacitance midpoint in current circuit can be transferred to the ground (GND) which is connected with it affect the control circuit, in the sampling circuit of the invention, the midpoint of the resistance R2, R3 is connected with ground all the way, but the midpoint of the generatrix capacitance C1,C2 and the ground are cut structure, so the high frequency noise of capacitance midpoint can not be transferred to the control ground. Aiming at obtain the generatrix voltage and the voltage difference between the generatrix capacitance C1,C2, the invention regards the ground as reference point, the midpoint of resistance R1,R2 is sampled to obtain the Vp, the midpoint of resistance R3,R4 is sampled to obtain the Vn, the midpoint of capacitance C1,C2 is sampled to obtain the VDelta, based on the three voltage value, the relative generatrix voltage and voltage difference between the generatrix capacitance C1,C2 can be obtained.