According to the sand - dust storm observation data of fifteen surface weather stations in Hexi area of recent 55 years, we applied linear regression and Mann - Kendall method to analyze the trend and mutation of the sand - dust storms in Hexi Corridor region. The research indicated that the sandstorms showed significantly decreasing trend. The spatial distribution characteristics of annual sandstorm days was obvious, the maximum value of average annual sandstorm days was 25. 5d, and appeared in Minqin. Sand - dust storm days appeared decrease mutation in the early 1990s in Hexi region. We found that there was significant positive correlation between dust storm days and gale days at the same time in each region of the Hexi Crridor, and that with temperature average was anticorrelation. The main reason for sandstorm days decrease was the climate warming and gale days reducing.