Marine aquaculture is an important way to utilize marine resources. In marine aquaculture, water quality directly affects the survival conditions and yield of the farmed species. Therefore, water quality monitoring is of great significance for the marine aquaculture industry. This paper designs a marine biological aquaculture water quality monitoring system based on the STM32 microcontroller. The system integrates DS18B20 temperature sensor, pH sensor and TS-300 turbidity sensor to achieve real-time collection of key water quality parameters. The system uses a 0.96-inch OLED screen for data visualization display, transmits data wirelessly to the mobile terminal through the HC-05 Bluetooth module, and realizes parameter over-limit alarm through the active buzzer. The program is written in C language, achieving real-time monitoring, remote transmission and alarm functions of water quality. The Proteus simulation test shows that all modules work stably, with a temperature monitoring variance of 0.43, pH value and turbidity variance of 0.75 and 0.76% respectively, and the accuracy meets the actual monitoring requirements. This system adopts a modular design, has low cost, is convenient to use, and can provide technical support for intelligent management of aquaculture.