Abstract: To address technical challenges in monitoring conservator tanks of oil-immersed transformers—such as oil mist interference, oil temperature fluctuations, and the high maintenance costs associated with traditional contact-based measurement methods—this paper proposes a real-time monitoring device for oil temperature and level based on ultrasonic non-contact sensing and LoRa wireless transmission. The device employs an ultrasonic sensor to perform non-contact measurement of the oil level in the conservator tank and incorporates a temperature compensation algorithm to correct for the influence of oil temperature on ultrasonic wave propagation speed, thereby ensuring measurement accuracy under varying operating conditions. Real-time data are transmitted via a LoRa wireless module to a remote monitoring platform, while the device also provides local display and abnormal-condition alarm capabilities. Field tests demonstrate that the device operates reliably across different transformer models, achieving an oil-level measurement error of ≤ ±0.2%, delivering timely alarm responses, and effectively enhancing the intelligence level of transformer operation and maintenance.