The invention discloses a system for impulse withstanding performance test of a gas-insulated impulse voltage generator unit. A cylinder body of a first lifting cylinder is fixed on a bottom plate of a sealed insulated tank, the top of a piston rod of the first lifting cylinder is fixedly connected with an insulation layer, a cylinder body of a second lifting cylinder is fixed on the bottom plate of the sealed insulated tank, the output end of an impulse voltage leading-in sleeve is connected to one end of a high-voltage conducting rod, a capacitor, an ignition sphere gap and a resistor are serially connected between the high-voltage conducting rod and an insulating rod, the insulating rod is sleeved with a conducting ring, a gap is formed between the conducting ring and the insulating rod, the conducting ring is connected to the top end of the second lifting cylinder through an insulating support, the conducting ring is grounded, and a charging sampling opening is further formed in the sealed insulated tank which is grounded. Impulse test under high voltage is realized, and test results can reflect gas-insulated disruptive discharge property of SF6 under the condition of an extremely non-uniform electric field.