Abstract:As the suitable habitats of the spotted alfalfa aphid, Therioaphis trifolii, were not clear and the prediction technology was fallen behind in Ningxia, we analyzed the suitable habitat of T.trifolii in a large scale based on GIS. The interpolation maps of T.trifolii population in Guyuan City in different periods were overlapped with the ecological regionalization map and digital altitude map, aimed to analyze the relationships of T.trifolii population density with its ecological environment and geographical distribution. The results showed, in the study area, the occurrence and distribution of T.trifolii had close relations with climate, geomorphology, and altitude. The suitable habitat of T.trifolii was located in the semi-arid plain area and semi-arid holly area at the altitude 1 501-2 100 m, while the most possible occurrence area was the semi-arid plain at the altitude 1 701-2 100 m. By combining the suitable habitat with the interpolation maps of T.trifolii population in different periods, the spatial dynamics of T.trifolii population in variety of ecological areas could be analyzed quantitatively.