The invention discloses a gas-isolation-based high-pressure liquid plunger pair. The gas-isolation-based high-pressure liquid plunger pair comprises a cylinder body adopting a hollow structure and a big plunger adopting a hollow structure, wherein the big plunger is arranged in the cylinder body, the upper outer wall of the big cylinder is in sliding fit with the cylinder body, and a first sealing cavity is formed between the lower outer wall of the big plunger and the inner wall of the cylinder body; and a liquid cavity is formed in the lower part of the cylinder body, and an isolation cavity communicating with the first sealing cavity is formed between the liquid cavity and the lower surface of the big plunger. The gas-isolation-based high-pressure liquid plunger pair further comprises a small plunger, of which the lower part is arranged in the big plunger and is in sliding fit with the inner wall of the big plunger, and a second sealing cavity is formed between the interior of the big plunger and the lower surface of the small plunger; the second sealing cavity and the first sealing cavity communicate with each other through at least one damping pore; and springs are connected between the upper part of the big plunger and the cylinder body. A liquid medium is isolated from a seal ring through a high-pressure gas film, and impurities are prevented from entering a friction pair, so that the service life of the plunger pair is prolonged, the liquid medium is prevented from leakage, and a working medium is prevented from corroding the plungers and a sealing part.