With the 40-year hail and thunderstorm data from meteorological stations over Northwest China, an analysis was made of the distribution characteristics of hails, and the relation with altitude, topography and concomitant thunderstorms. The causes of frequently occurring hails in Northwest China are discussed. The result indicates that hails in this area are concentrated mainly around three areas; the occurrence of hails is highly correlated with thunderstorms and altitude with the correlation coefficients being 0.78 and 0.84; and in the last 10 years hail disasters decreased greatly. Considering meteorological factors and topography, five source areas of hails are pointed out.