Head Mounted Display (HMD) has been widely used in the area of wearable computing, augmented/virtual reality etc. The different image sources and optical subsystems of HMDs result in the diverse comprehensive display properties and optical properties. The traditional method to evaluate a HMD is modular transfer function. It requires special instruments, software and professional backgrounds knowledge, and thus leads to the lack of usability when it applied by common users. On the basis of human transfer function and Fitts’ model, in this paper we proposed an evaluation method, which has the advantage of easy applying. We evaluated this method targeting at a commercial HMD and a custom HMD, and the result shows that our method has a high usability.