Abstract: Based on GIS techniques, the interpolation maps of Therioaphis trifolii popu
lation on the arable lands in Yuanzhou District of Guyuan City in differen
t periods were overlapped with the ecological regionalization map and digital al
titude map, aimed to analyze the relations of T. trifolii population density
 with its ecological environment and geographical distribution. In the study are
a, the occurrence and distribution of T. trifolii had close relations with c
limate, geomorphology, and altitude. The suitable habitat of T. trifolii in
the District was located in the semi-arid plain area and semi-arid holly area
at the altitude 1440〖KG-*2〗-〖KG-*7〗2000 m, while the most possible occurrenc
e area was the semi-arid plain at the altitude 1600〖KG-*2〗-〖KG-*7〗1800 m. B
y combining the suitable habitat with the interpolation maps of T. trifolii
population in different periods, the spatial dynamics of T. trifolii populati
on in variety of ecological areas could be analyzed quantitatively.

Key words: Therioaphis trifolii, suitable habitat, geographic information system, regional trial, testing-site discrimination ability, testing-site representativeness, relative least significant difference, experiment precision.