The utility model discloses an oil and gas well workover fluid pressure-bearing blocking evaluation tester. The tester comprises a pressure kettle and a clamping device, wherein the pressure kettle is provided with a kettle body and a kettle cover; the clamping device is mounted on the kettle body in a detachable and sealed manner, communicated with the pressure kettle and used for clamping a core; a pressurizing port is arranged in the middle of the kettle cover; the clamping device comprises a casing, an annular sleeve, a clamping cover, a cushion block and a ejecting rod, the annular sleeve divides an inner cavity of the casing into an inner cavity body and an annular cavity body, the clamping cover is connected to one end, which is far away from the kettle body, of the casing, the cushion block is arranged in the middle section of the annular sleeve, and the ejecting rod is partially sleeved with the annular sleeve; the kettle body is provided with a liquid inlet communicated with a pressurizing device; the casing is provided with a pressure exerting port communicated with the pressurizing device; the clamping device is provided with a drain hole penetrating through the cushion block and the ejecting rod and also provided with a drain port. The clamping device clamps the core, so that different parts of the core are pressurized differently; the drain hole extends along the ejecting rod to be communicated with the outside to form a differential pressure and filtration passage, the downhole high-temperature high-pressure pressure-bearing blocking and filtration performance is well simulated, the performance of a workover fluid is evaluated, and the scientific basis is provided for scientific research.