Abstract: By use of the recent 30 years’ precipitation data of Chengdu from 1981 to 2010, an analysis is made of the time change feature of the precipitation time. The results show: the overall precipitation sees a slight decreasing trend in the area under investigation, the recent ten years in particular, sees an accelerated decrease in this respect; the precipitation time sequence exist three primary period changes at 6.5a, 12a and 19.5a respectively, of which the periodic oscillation of the 19.5a energy is the most powerful.