AIM:To develop a type of measuring instrument which is capable of automatically,accurately measuring the varying degrees of compensatory head posture. ·METHODS:According to the physiological characteristics of human head and neck,we put the liquid compass in the helmet for the development of automatic compensatory head posture measuring instrument,for the electronic liquid compass can accurately record different axial range of activities. The measuring instrument was mainly composed of inductor (liquid compass department),helmet,data processor and voltage regulator devices. The range of the activity of head and neck was perceived by the inductor embedded in the helmet,the change was conducted to the data processor through a data line,and the result was recorded after instant data-processing. This result was compared with the range on the dial installed on the model to verify the accuracy of the data. ·RESULTS:The helmet was put on the model’s head and the data was recorded on the automatic compensatory head posture measuring instrument at that time,then the model’s head was turned in three dimensional directions; and the data were recorded respectively. The difference between pre-and post-rotation was the final data. To check the data against the dial on the model,we found that the error didn’t exceed 1 degree. ·CONCLUSION:The automatic compensatory head posture measuring instrument plays an important role in clinical practice. It is a simple way to accurately measure three-dimensional orientation of head and neck,and it has a much larger measuring range than the physiological range of the activity of human head and neck. It has won the National Invention Patent of China (Patent Application No. 200820022027.0).