The water quality ammonia nitrogen detector is a detection device suitable for industrial wastewater, aquaculture, river monitoring, swimming venues and other fields. Combined with rapid colorimetric detection reagents, it can "quickly, simply, accurately and stably" detect the ammonia nitrogen content in water bodies; The device is equipped with multiple light sources corresponding to different detection wavelengths, which can simultaneously meet the needs of Nessler's reagent method and salicylic acid method for detecting ammonia nitrogen content in water. The Nessler's reagent method refers to the environmental standard HJ 535-2009 "Determination of Ammonia Nitrogen in Water Quality - Nessler's reagent spectrophotometric method", and the salicylic acid method refers to the environmental standard HJ 536-2009 "Determination of Ammonia Nitrogen in Water Quality - Salicylic Acid spectrophotometric method". The device has a beautiful appearance, a simple operating interface, and an accurate detection system, which helps users obtain fine data and analyze water conditions more accurately and effectively, avoiding losses in a timely manner.