Based on the actual snow disaster data over the Qinghai plateau from 1951 to 2008, the mortality rates of livestock caused by snow disasters are calculated, referring to the proportion of droughts of various levels in SPI (Standardized Precipitation Index) calculation to determine the threshold values for the snow disaster of a certain level. The indexes for snow disasters are devised based on the actual disasters and tested on several typical snow disasters. The results show that the indexes are in accord with the standards of DB63 In the pasturing area of the Qinghai plateau, it is a more reasonable and practical method to establish the indexes of snow disasters and to determine the level of a snow disaster by using the mortality rate of livestock caused by snow disasters.