According to the characteristics of the variable motion trajectory and postures during the floating buoy operation that affect the reliability of the sensor, the floating buoy attitude measurement system based on three-axis MEMS gyroscope, accelerometer and magnetoresistive sensor is designed. This paper presents the hardware structure and software algorithm flow of the design system. It use, quaternary method and PI regulation algorithm to perform attitude algorithm and data fusion. The systematic error is corrected by ellipsoid fitting and threshold filtering for error compensation method. Experimental results show that the proposed design is more effective in the measurement of motion attitude which has small static error and good dynamic anti-interference performance to meet the basic needs of attitude measurement of ocean drift buoys.