The oil pillow of the power transformer avoids the direct contact between the insulating oil and the air by arranging a synthetic rubber chamber on the surface of the inner insulating oil. The rubber chamber is made of rubber with good oil resistance and rain resistance. The air in the rubber chamber communicates with the outside air through a respirator equipped with silicone, thereby preventing the deterioration of the rubber. The device for indicating the oil level in the oil pillow of the power transformer is an electromagnetic oil level gauge, and the maximum and minimum displacement of the oil level float position is divided into 10 scales and marked on the dial instead of dividing the oil amount into uniform scales. When the oil level of the oil pillow of the power transformer drops to 0 for some reason, the contact in the oil level gauge closes and alarms.