In order to ensure the whole field of view parallax can be measured, the charged-coupled device (CCD) camera which replaces eye must be located at the observation position (eye point) because the machine vision is not as flexible as the human eye, when the parallax of helmet mounted display is measured automatically. A pattern search method was proposed to make CCD camera locate at the observation position automatically in the optical plane of the helmet mounted display (HMD). Thus, the parallax of the helmet mounted display in the whole field of view can be measured automatically. The principle of the automatic measurement system was discussed in detail, and the process of CCD camera aligning observation point automatically was introduced in detail. Then the measurement precision and efficiency were also analyzed experimentally, as well as the alignment accuracy and repetitive positioning accuracy. The experimental results show that the method can ensure the CCD locate at eye point accurately with high efficiency. The positioning accuracy is ±0.071° .Compared with the pendulum method to measure parallax, it has high measuring efficiency and high repetitive positioning precision.