Based on the daily precipitation and daily sunshine hour data from 1972 to 2011 at meteorological observation stations, a new monitoring index (Daily Autumn Rain Index, DARI) of Huaxi autumn rain is defined. The temporal spatial applicability of DARI is analyzed and the intraseasonal variability is researched too. Based on the actual meteorological disaster records the strong years when more autumn rains occurred in the related provinces are indentified. Compared with the new monitoring index (DARI) it is found the DARI and the strong years are consistent in most cases. Of course, there exist some inconsistencies as well. In some years the monitoring indicators show the strong side, but there are no disaster records. Some literatures and the actual rainfall data indicate that the monitoring index matches with the actual situation. In some years there are disaster records, but little autumn monitoring index. Further research indicates that the disasters tend to occur only in a few days, in most of the remaining time it is normal or weak, so there is no reflection in the year index. In climatic mean status, the intensity of Huaxi antumn rain weakens with fluctuation. The period from 6 to 16 September is the strongest period of the three. There is obvious interdecadal variation for the interseasonal variation of DARI. There are two significant periods in 1970s, three in 1980s, three in 1990s and three at the beginning of the 21st century. The application case shows that DARI can demonstrate the whole variation process of occurrence, development and disappearance of Huaxi autumn rain.