This paper designs a deep-sea attitude system based on the MPU9250 nine-axis data sensor to solve the problem of deep-sea instrument attitude monitoring, and conducts experimental tests to verify it. The system uses STM32F103 as the main control chip to collect MPU9250 nine-axis data, and quickly calculate the current real-time motion posture through software algorithms. And use the three-axis acceleration data to calculate the inclination angle with the natural coordinate system Z axis. The system is designed with a storage module and a real-time clock module, which can record the movement posture and tilt angle of the equipment in the storage module in real time. And according to the environmental requirements of deep-sea instruments, combined with the finite element design method, design the deep-sea pressure tank. Experimental results show that the attitude system can detect the attitude and inclination of deep-sea instruments with an accuracy of 0.5°, and the pressure resistance can reach a depth of 4000 meters.