An enhanced algorithm on iris image quality assessment was proposed. For the disturbed iris images captured by the iris recognition system utilized for long-distance moving iris recognition, the quality indices of the resolution, availability, and contrast of the region of interest of the single frame iris image were quantified. And the joint weighted quality scores of sequential images were calculated, which were used to effectively evaluate the usability of iris image sequences and screen out the unqualified low-quality iris image sequences. Experiments show that the algorithm improves the accuracy and reliability of image quality assessment of the iris recognition system, which can effectively improve the robustness and recognition efficiency of the system.