The invention discloses a transformer oil-gas separation device based on a hollow photonic crystal fiber, which belongs to the technical field of separation and detection of mixed gas from oil with gas dissolved therein in transformer oil. In the transformer oil-gas separation device, a common solid optical fiber, which is same or approximate in diameter with the hollow photonic crystal fiber and is single-mode or multi-mode, is connected between two ends of the hollow photonic crystal fiber to form a low-loss-restraint light transmission path. A row of holes are formed on the surface of the hollow photonic crystal fiber in the axial direction and single hollow photonic crystal fiber forms a gas chamber of failure gas, thereby greatly reducing the volume of the gas chamber, so that a sensor can be built-in the transformer. One connecting end of the hollow photonic crystal fiber and the solid optical fiber is formed in a direct melt-welding manner, and at the other connecting end, an inorganic ceramic tube sleeves the connection point between the common solid optical fiber and the hollow photonic crystal fiber for achieving mechanical alignment. The transformer oil-gas separation device achieves surface drilling technology on hollow photonic crystal and inorganic thin film permeating separation at the connection point and can increase the efficiency of oil-gas separation.