Abstract: Based on the observation data from March 2004 to February 2008 in the main urban area of Chongqing, the diurnal, monthly, seasonal and annual variations of ultraviolet radiation intensity were analyzed in order to service the operational forecast and the objective forecast technique. The results indicate that the maximum value of daily average radiation intensity occurs during the period from 1:00 PM to 2:00 PM. The daily average radiation intensity is the highest in July and August with the largest probability of the fourth grade (radiation grades), while the lowerest in January and December with less than the third grade. The largest seasonal average radiation intensity appears in summer, followed by spring and autumn, and the lowest in winter. The annual average radiation intensities in 2004, 2006 and 2007 are almost the same, while that in 2005 are lower.