According to the official history,during the period from 300 to 1909 A.D.,China witnessed a total of 436 dust storms,which lasted a total of 901 days.The product td (t,the number of dust storms in every ten years,d,the days the dust storms lasted),may be used as an index of frequency of dust storms in different periods,and may also be regarded as an index of aridification degree of soil environment.Dust storm frequent periods,≥ 30 years,were distributed in 480～509,1170～1219,1690～1729 and 1840～1879 A.D.These periods with td values ≥ 25 corresponded to the cold periods in the history.Cold and dry periods are prone to triggering dust storms.During the 1610 years studied,the average dust fall for every year is about 0.54 cm.Aeolian process of the loess is still going on nowadays.