The in-situ nutrient analyzer is a chemical analyzer suitable for shallow water areas. Dissolved nutrients including ammonia (NH3-N), nitrite (NO2-N), nitrate (NO3-N), phosphate (PO4-P) and silicate (SiO2-Si) can be measured. It is small in size, easy to carry and apply to install on buoys, shore stations, survey ships and other monitoring platforms. It is suitable for ocean, estuary, river, lake and other aquatic environments. It provides high-precision, continuous and stable data for eutrophication research, phytoplankton growth research and environmental change monitoring.