Abstract: According to the testing requirements of China's national environmental protection standard HJ 970-2018 “Water Quality—Determination of Petroleum—Ultraviolet Spectrophotometric Method”, the principle of ultraviolet (UV) spectrophotometric oil measurement was analyzed. Through the automated and integrated design of the injection system, extraction system, adsorption and filtration system, and detection system, a new fully automated UV oil analyzer was developed. The instrument's structure, operating principle, application, and maintenance were described in detail. The instrument was calibrated according to JJF (Min) 1141-2023 “Calibration Specification for Ultraviolet Oil Content Analyzers”. Over the range of 0.0 to 16.0 mg/L, the instrument exhibited a linear correlation coefficient of 0.9999. For measurements not exceeding 2 mg/L, using 1.0 mg/L as an example, the indication error was −0.042 mg/L. For measurements exceeding 2 mg/L, using 4.0 mg/L, 8.0 mg/L, and 16.0 mg/L as examples, the indication errors were −3.6%, −2.2%, and −1.7%, respectively. Additionally, the instrument’s repeatability, minimum detectable concentration, zero drift, and indication drift were calibrated. The results of these calibration experiments verified the instrument’s excellent performance. By using the fully automated UV oil analyzer, environmental protection workers can reduce workload, improve efficiency, minimize exposure to organic hazards, and ensure accurate and efficient environmental monitoring.