The deep-sea environment, an underexplored and mysterious realm, is not only home to exotic creatures, but also key to studying Earth’s history, climate change, and marine ecosystems. Its extreme conditions pose challenges for scientific investigations, and the distribution and transformation of nitrates are particularly important for understanding ocean productivity and global climate change. To this end, a low-power seawater nitrate profile measurement method based on ultraviolet spectroscopy technology is proposed for the detection of nitrate concentration in the marine environment. The sensor directly measures the characteristic absorption peaks of nitrate by ultraviolet spectroscopy, avoiding the dependence of traditional chemical analysis methods on reagents. The hardware design adopts a series of low-power modules, such as a low-power STM32L1 microcontroller and ultraviolet LED light source, to ensure the stability and low energy consumption of the sensor in long-term monitoring of the deep sea. In addition, the sensor integrates temperature compensation and organic matter compensation algorithms, which can effectively reduce the influence of ambient temperature fluctuations and dissolved organic matter in seawater on measurement accuracy. At the same time, the precision and recovery of the sensor experimented, the precision of the sensor was measured many times at the nitrate concentration of 500ug/L, the RSD was only 4.52%, the recovery rate of the 15 spike experimental samples prepared by the standard preparation of wheat island seawater was between 90%~110%, and the recovery rate of the 15 samples was 109.24%, and the lowest was 97.73%, which were within the requirements of the national standard. Nitrate sensors provide highly accurate nitrate concentration measurements at different depths and environmental conditions, in good agreement with traditional chemical analysis data. Its good power consumption and profiling function provide reliable data support for the study of deep-sea nitrogen cycle and carbon sink, which is of great significance for global climate change prediction.