As vehicle safety research advances, the need for precise measurement and analysis of vehicle motion posture during crash tests has significantly increased. This study introduces a method that relies solely on accelerometer data to determine vehicle motion posture during crash tests. By addressing the limitations of traditional gyroscopes' measurement accuracy under impact loads, we explore the potential of using multiple accelerometers to obtain high-precision angular velocity data. To achieve this, the paper proposes an efficient algorithm for processing data from multiple accelerometers, successfully determining the vehicle's motion posture during crash tests. The effectiveness and accuracy of the proposed method are validated through real vehicle crash tests. The findings suggest that this method provides highly reliable data support for analyzing vehicle crash safety and offers a new engineering approach for future evaluations of vehicle safety performance.