The traditional method of manually sampling water quality is time-consuming, labor-intensive, inefficient, and susceptible to external environmental influences. In order to improve the stability and ease of control of fish pond water quality detection, an online water quality monitoring system based on STM32 is designed in this article. The STM32-based fish pond water quality detection system uses the STM32 microcontroller as the core controller and consists of six parts: power supply module, liquid crystal display module, water turbidity sensing module, PH value sensing module, and wireless WiFi module. The test results show that the detection system can realize online detection of target water quality by viewing it on the web page, and can detect the PH value and turbidity of fish pond water in real time. It has the characteristics of low cost, high availability and strong practicability. It is for the realization of fish pond water quality. Pond water quality monitoring and intelligent management provide a better solution and are of great significance to promoting aquaculture.