The invention relates to a device and a method for realizing auxiliary injection by using a natural gas well oil jacket pressure difference. The device comprises a gas driving head (a), a connecting shaft (b) and an auxiliary booster pump (c); the gas driving head (a) is connected with the auxiliary booster pump (c) through the connecting shaft (b); and the gas driving head (a) converts the oil jacket natural gas pressure difference to driving force, and drives the auxiliary booster pump (c) to supercharge auxiliaries through power transferred by the connecting shaft (b). The device has the following beneficial effects: driving gas is acted and exhausted into a production pipe without generating leakage and emission; although the driving gas is flammable and combustible mediums, the equipment operation is not influenced; only if the gas well production exists, the driving gas is inexhaustible; in addition, a high-pressure difference gas driving pump is skillful in design; the oil jacket pressure difference is reasonably used without needing a power supply, so that the well opening injection is convenient; the driving head resists high pressure; the driving gas is high in pressure without needing the pressure adjusting treatment; and a mated module is combined to conveniently realize automatic injection.