In this paper, the crustal thickness of the western region of Gansu province is inverted by means of gravity data and single crustal model. According to Airy isostatic hypotheses, a computation of isostatic compensation has been made and a map of M surface and a map of isostatic anomaly drawn up.
The force source formed on the crustal variation belt of the western region of Gansu province is briefly discussed.In the light of the historical data of earthquakes, the relationship between crustal structure and isostatic anomaly and the earthquakes is discussed.