In order to measure the perceptual quality of images, it is important to find suitable Image Quality Assessment (IQA) methods. Compared with the traditional objective IQA methods, the subjective IQA methods can more truly reflect users’ subjective feelings on image quality. However, the evaluation steps in subjective experiments will interfere with the process of subjects viewing images. We propose a non-intrusive IQA method based on eye-tracking technology to overcome the shortcoming. Through subjective experiments, we collect the eye movement data of subjects and calculate four main features from them. The analysis results of the eye movement parameters indicate that users pay attention to different areas of images with different qualities. Then, we use the eye movement parameters to design the Non-Intrusive Subjective (NIS) IQA algorithm which is a new subjective quality metric of images. Experimental results reveal that the validity and feasibility of the proposed metric.