In view of the current problems of sea buoy dissolved oxygen (DO) sensors such as high power consumption, complex calibration processes, etc., a STM32-based DO monitor with low power consumption and high performance was designed, which realized the automatic calibration of the DO sensor through infrared calibration design. With the design, the DO value can be accurately calculated using the combination of single power data acquisition circuit and multi-channel STM32 ADC. The design makes use of the input capture function of STM32 to decode the infrared remote control signals, realizing the slope calibration of voltage-DO curve, and effectively avoiding the tightness risks of buoys caused by the frequent disassembly due to calibration of oxygen. Power saving mode meets the requirements of low power consumption and can improve the power supply duration of the battery. The RS485 port integrating with the MODBUS protocol can achieve remote communication, and lay a solid foundation for remote monitoring. Experimental results show that the DO acquisition accuracy of the monitor is higher, and monitor can run continuously for 5-6 days under no-light condition. This design can greatly improve the stability and tightness of buoys, and provide great convenience for the working staff with the advantages of low cost, small volume, and easy installation.