The invention discloses a transformer oil temperature detection system, and the system comprises an oil tank. An iron core is provided with a high-voltage coil and a low-voltage coil in a winding manner. The upper part of the high-voltage coil is connected with a high-voltage insulating bush on the oil tank, and the low-voltage coil is connected with a low-voltage insulating bush on the oil tank. The upper part of the oil tank is also provided with a tapping switch which is used for adjusting the number of turns per coil. The oil tank contains transformer oil. The interior of the oil tank is provided with a plurality of ceramic heating pieces, and the iron core, the high-voltage coil and the low-voltage coil are provided with a plurality of thermal radiation optical fiber sensors in a winding manner. The thermal radiation optical fiber sensors are respectively disposed at the upper, central and lower parts of the iron core, the high-voltage coil and the low-voltage coil, wherein the number of the thermal radiation optical fiber sensors is 2-4. The ceramic heating pieces are cross-shaped, and the interior of each ceramic heating piece is provided with a heating core, wherein the heating cores are connected with electrodes. The exteriors of the heating cores are provided with ceramic layers, and the upper parts of the heating cores are provided with a plurality of core heads which are embedded into the ceramic layers. The beneficial effects of the invention are that the system is simple in structure, is convenient to use, is accurate in detection, truly detects the changes of oil of an oil immersed transformer in actual operation.