One of prominent features of traditional oasis cities is remote and closed from each other. After reforming and opening, the rapid regional development and improvement of transportation promotes that urban agglomeration capability of oasis cities amplified obviously and contact with each other strengthened widely. The measurement on urban agglomeration indexes of 87 cities and towns in Xinjiang in the period of 1990-2002 is based on the synthesis of four aspects, which are population growth, economic development, urban construction speed and melioration of dweller's living. The results of analysis can draw four conclusions: 1) the polarization of urban agglomeration index shows that the gap of urban agglomeration capability among Xinjiang cities and towns is more widened in the past 12 years; 2) central cities, such as Urumqi, Karamay, Korla and Kashgar, are bulging their agglomeration functions rapidly and seven urban economic regions are forming; 3) the aggregation force of cities and towns which located in agglomeration shadow area of central cities has reduced, including the exurb of largest city, Urumqi, and outskirts of middle-size cities, such as Shihezi, Yining and Kashgar; 4) there are apparent spatial differences between northern and southern Xinjiang. The polarization of agglomeration capability of the northern Xinjiang is stronger than that of the southern Xinjiang. Three factors deeply effect the change of urban agglomeration capability in Xinjiang, which are the enlargement of oasis, exploitation of petroleum resources and adoption of policies. The trend of urban agglomeration development can give some illustrations to urbanization and urban system in Xinjiang. Central cities should be the leading actor in the urbanization of Xinjiang and some urban clusters can be form in the near future, which are represented by Urumqi Metropolitan area and urban region composed by Kuitun, Wusu and Dushanzi. Specialization and diversification will become the features of cities functions and the special layout will make for the integer advantage of urban system of Xinjiang. The developing model in the northtern Xinjiang is urban and rural incorporation and the model in the southtern Xinjiang is regionally drived by central cities and rapid-growing axis.