The invention relates to an isolated gas lift drainage method. The isolated gas lift drainage method comprises the following steps: S1, a mounting pipe string is assembled, specifically, a first starting device, a punching gun (400), a second starting device and an isolated gas lift packer (100) are sequentially connected; S2, well lowering and punching are conducted, specifically, the mounting pipe string is lowered into the specified position from a production well pipe, and the first starting device controls the punching gun (400) to implement punching on the production well pipe; S3, upward lifting and setting are conducted, specifically, the mounting pipe string is upwards lifted, the isolated gas lift packer (100) is upwards moved to the punching position, and the second starting device controls the isolated gas lift packer (100) to conduct setting; S4, release and upward lifting are conducted, specifically, after setting, release is achieved, and the first starting device, the punching gun (400) and the second starting device are recovered to complete mounting; and S5, gas filling for liquid discharging is conducted, specifically, high-pressure gas is filled to discharge accumulated liquid. The mounting pipe string only needs to be lowered once, punching and setting are sequentially implemented, then the remaining mounting pipe string is lifted out, then mounting can becompleted, the process steps are simple, and mounting position control is more accurate.