The invention relates to the field of a method or equipment for installing, maintaining, repairing or dismantling electric cables or wires, and discloses a rain and snow resistant insulator and a cross arm replacing device and replacing method, the rain and snow resistant insulator comprises a main cross beam, a fixing device and a wire lifting device. The fixing device is arranged at the middle position of the main cross beam; A lead lifting device is fixed on both end of that main cross beam through a fixing seat, the lead lifting device comprises a screw rod, an umbrella skirt insulation part and a lead fixing part, wherein the umbrella skirt insulation part is fixed on the screw rod, and the lead fixing part is fixed on the umbrella skirt insulation part. The invention solves the problem that sudden rainfall in the operation process cannot guarantee the safety of the line or the operator, When the insulator and the cross arm are replaced, no matter when the weather changes, the line cannot lose the insulation between the phase and the ground, and when the weather changes, the operation personnel can be evacuated immediately, which ensures the safety of the operation personneland the safety of the line and the equipment.