The WM1800S outdoor small automatic water quality monitoring system (hereinafter referred to as the micro-station) is an outdoor integrated station, which has the characteristics of small footprint, convenient installation and so forth. It meets the requirements of the main building and external supporting facilities required by the automatic water quality monitoring system. It has absolute advantages in the sites of difficult station buildings and the parks where high-density water quality monitoring is required. The micro-station can simultaneously monitor nine conventional parameters in line, including pH, dissolved oxygen, conductivity, turbidity, water temperature, permanganate index, ammonia nitrogen, total phosphorus and total nitrogen. It can realize automatic collection and processing of water samples, real-time and integral-point analysis of five parameters, analysis of water quality instruments, and automatic cleaning and algae removal of pipelines, so that the maintenance workload is small. Covering an area of about 1m2, the system can be installed easily and is equipped with integrated air conditioner to maintain constant temperature and humidity and ensure the stable operation of the system. The outdoor cabinet has a protection level of IP54 or higher, is provided with the functions of rain/lightning protection, power failure, flooding, smoke, temperature and humidity alarms, and can be unattended around the clock.