Being stuated in the west part of Sichuan Basin, Penxi plain is the greatest plain of south-western China and cover an area of 10,000 squar kimloeters, According to geomorphic structure, Penxi Plain is depression with Longmanshan fracture as its east margin and with Longquanyi fracture as its west margin. The principle strata of this plain are chengdu clay and Yaan gravel of Quaternary Epoch. The main geomorphic exogenetic processes are normal weathering and fluvial ersion and deposition. According to geomorphology, this plain may be divided into three subregions, They are the Fujiang alluvial valley and terrace in the north, the complex alluvial-diluvial-fan of Minjiang-Tuojiang in the middle, and the composite alluvial plain of Minjiang, Qingjiang and Daduhe in the south.

The city and town system of Penxi Plain is compoes of four types of settlements, The metropolis Chengdu as the primate, Miang, Deyang, Leshan and Chengdu as four central cities, 28 county-towns and hundreds of fairs spreading all over the plain. The principle of this system is the combination of masteting, transportation, history and administraction while geomorphology is the main physical factor of this system. Primate Chengdu is situated in the center of plain and central cities of Chengdu and Deyang covering the whole area of Fujaing alluvial valley plain and terrace, and Leshan is situated in the center of Minjiang-Qingyijiang-Daduhe alluvial plain. A great number of counties, towns and fairs are scattered in river valley of small basin. On the otherhand, a number of towns are situated on the margin of the plain because the margin is the bordering line of two physiAnogaphic regions.

Anthoropogenetic geomorphology and manmade superinduced landform are two main charcteristics of urban geomrphology in  Penxi plain. Anthropogenetic geomorphic forms are repressented by the builing-transportaition systems and the landforms resulting from the mass flus and energy flus in urban area. How to dispose the solid waste of cities and towns is the key problem of urban ecologic geomorphology. There are about 1000tons of garbage per year from Chengdu, hence a hilly region of garbage heaps was built in the outshirt. Refuse incineration will be built in the short future. Earthquake is the potential disaster of Penxi. The main natural disaster of Penxi is the serious flood damage. The knickpoint line on the Longquanyi fracture has the high frequency of floods. The knickpoint line is coincided with the line of the different strata resistence. There is plan to derive water in the upper part of Mingjiang River. It is a good means to solve the insufficiency fresh water problem of the urban adrea in Penxi Plain.