An AC withstand voltage tester comprises a voltage-regulating insulated gate bipolar transistor module, a boost transformer, a programmable logic controller and a current transformer, wherein the power input terminal of the voltage-regulating insulated gate bipolar transistor module receives voltage from an AC grid; the power output terminal of the voltage-regulating insulated gate bipolar transistor module is connected to the boost transformer; the control terminal of the voltage-regulating insulated gate bipolar transistor module is connected to the programmable logic controller; the current transformer is connected in series with one of the power input terminal of the voltage-regulating insulated gate bipolar transistor module, the power output terminal of the voltage-regulating insulated gate bipolar transistor module and the power output terminal of the boost transformer, so as to detect the current value; and the current transformer sends the detected current value to the programmable logic controller. The AC withstand voltage tester of the present invention solves the problems of unsafe operation, low output precision and no intelligent auto-control in the prior art, so that the AC withstand voltage tester can guarantee the safety of operators and tested equipment, and can output expected voltage values precisely.