Marine environmental pollution in China has become increasingly serious with most pollution being caused by inorganic nitrogen and phosphate. An efficient monitoring and fast measurement of oceanic nutritive salts, especially nitrate salt, has gained greater significance . The traditional detection methods, mostly utilizing analytic chemistry, tend to be more suitable for laboratory testing. Infrared absorption spectrum is important for real-time monitoring of marine nutrients, since it not only makes up for the shortcomings of traditional methods, but also provides fast and simultaneous monitoring of various nutrients at the same time. However, marine nutrient concentrations in seawater are at particularly low level. As a result, normal IR detection is difficult to meet the requirements due to the limitation . This paper aims to utilize surface enhanced infrared absorption effect (SEIRA) of nanomaterials, making the detection of ocean nutrients with IR adsorption possible.Surface-enhanced infrared absorption (SEIRA) of nano-materials is expected to improve dramatically the sensitivity of traditional FTIR and positively achieve the goal of swift measurement of oceanic nutritive salts. Nano silver (Ag) has remarkable surface plasmon resonance effect that could help achieve high SEIRA. Diamond with extraordinarily strong anti-corrosion property is suitable for infrared window.In this paper, silver/diamond powder (Ag/DP) composites were prepared via pyrolysis of silver nitrate (AgNO3) on silicon substrate. Proportion of Ag and DP (nAg∶nC) on the IR adsorption of NaNO3 solution was investigated. Our results showed that Ag/DP composites significantly increased the IR adsorption of two individual antisymmetric stretching mods of NO-3. When nAg∶nC was 2∶1, Ag/DP composites indicated the strongest enhancement of IR adsorption of NaNO3 solution. This paper will be an important contribution for real-time, long-term and continuous testing of marine nutrients. It will also provide important data support for marine disaster prevention, marine pollution control and other areas of the marine environment management.