The invention relates to an oil supply system used for a seabed oil charging cable, comprising two groups of oil charging units which are arranged on two ends of the oil charging cable; each group of the oil charging unit comprises an oil storage tank, a positive displacement pump, a tee regulating valve, a flow metering module, a pressure transducer, a temperature sensor and a vacuum pump. The oil storage tank is communicated with the end of the oil charging cable through a connection pipeline; the positive displacement pump, the tee regulating valve, the flow metering module, the pressure sensor and the temperature sensor are successively arranged on the connection pipeline between the oil storage tank and the oil charging cable. The vacuum pump is connected to the oil storage tank through the pipeline; the positive displacement pump, the tee regulating valve, the flow metering module, the pressure sensor and the temperature sensor are connected to a console. Compared with the prior art, the invention can realize small flow oil supply under a normal working condition in order to satisfy the big flow oil supply under an emergency condition, strive for more time for the power line repair, eliminates the air inside the oil line and reduces the system fault sources.