In this paper, the development of a portable, multifunctional water quality monitoring system for aquaculture that is based on IoT technology is presented. The system integrates a main control module, sensor module, Human Machine Interface (HMI) module, Wi-Fi module and power module, and is equipped with system software based on Real Time Operating System (RTOS) for scheduling tasks. The main control module collects crucial water quality information, including water temperature (WT), dissolved oxygen (DO), ammonia nitrogen (NH3-N), and pH, through the sensor module and facilitates data interaction with the HMI module. The proposed aquaculture water quality evaluation model utilizes water quality parameters as input to assign a grade based on the evaluation result. These parameters are transmitted wirelessly to the OneNet cloud platform using Wi-Fi modules, enabling users to remotely monitor the water quality through a visual interface. The system structure has been meticulously designed to accommodate both portable and fixed-point remote monitoring applications. The experimental results demonstrate that the system is accurate, stable, and cost-effective, providing a reliable and efficient solution for intelligent aquaculture in small and medium-sized enterprises.