The virtual field of view (VFOV) is an important design parameter of augmented reality (AR) optical systems. The measurement method and the standard used to assess virtual image edges are not clearly established. A measurement method for determining the VFOV of an AR optical system is investigated in this study. First, the method is designed to calculate the VFOV of the AR optical system based on image acquisition by the camera system, and the maximum virtual image displayed by the AR lens sample at different virtual image view distances (VIDs) is acquired. Then, the effects of different pixel luminance statistical parameters as luminance thresholds in the determination of the virtual image edge and different VIDs on the VFOV measurement results are analyzed. The results show that there is a difference of 11° (V)×7° (H) in the VFOV measurements obtained for the six types of statistical parameters. Further, the maximum fluctuation range in VFOV for different VIDs at the same luminance threshold is found to be ±2.630° (V)×±1.685° (H) and the minimum is ±0.228° (V)×±0.360° (H). It is concluded that the luminance threshold of edge pixels is highly correlated with the VFOV results. The influence of the VID on the VFOV measurement is found to be significantly less than that of the luminance threshold. A threshold value of 64% of the arithmetic mean of the pixel luminance is used in this study as the VFOV results obtained with this value are the most stable, with a relative fluctuation of only 0.91%. The proposed measurement method and the process can be considered to be highly significant for AR optical systems.