For the issues of false oil level in the measurement of the transformer oil conservator, the aging of the insulating oil and oil compensating after power failure, the paper proposes an oil level measurement and charged oil compensating device of transformer based on pressure sensor. Through installing dual pressure sensors in the oil storage tank drain pipe and using two-point differential pressure algorithm to accurately measure the oil level, The device can reduce repeating maintenance caused by false oil levels. Then, through the separation of oil flow and pump body, vacuum cycle exhaust system, separation of oil inlet and oil filling process, the oil storage of the transformer oil tank can be realized without power failure. The device can reduce the number of power failure maintenance, and effectively improve the overall operation reliability and user experience of the equipment. Through the transformation and comparison of the existing transformer oil conservator of the State Grid Baoding Power Supply Company, the measurement accuracy and practicability of the device were verified.