Clear sky visibility has been found to decrease over land globally for the past several decades. The largest decreases have been in Asia, and these decreases have accelerated over the past decade. In China, fine particle pollution and fog-haze, which are closely related to visibility, have raised intensive concerns in recent years. In this review, on a basis of introduction of the factors affecting atmospheric visibility, quantitative relationships between visibility and PM 2.5 mass concentration and chemical composition are reviewed, with a focus on the development and revision of IMPROVE extinction algorithm, and major results in different regions in the United States of America based on its applications. Finally, the related researches conducted in China in last ten years are briefly summarized, including the major findings and some important research programs.