Abstract: A research of the atmospheric visibility is of great importance to ensure traffic safety of a city and reform atmospheric environment.In this paper,based on the data of the horizontal visibility,in Guangzhou,the variation with time and space of the visibility,the formation reasons of the low visibility and the effect of the urban development on the visibility have been analysed.The result of analysis shows that the urban developmen results in the decreasing of the high visibility(7-8 grade on the visibility range) and thet increasing of the general visibility(5-6 grade).