Urbanization is an integrated process of regional population growth and socio-economic development. The most notable feature of urbanization is the urban expansion in space. Built-up area information was extracted from Landsat ETM⁺ images using decision tree classification method based on RULEGEN. Pearson's chi-square test and Shannon's entropy model were used to calculate the degrees of freedom and sprawl of urban expansion. Results show that the urban expansion had higher degrees of freedom and sprawl, moreover, it was imbalanced in different directions apparently in the resent 8 years. The degrees of freedom and sprawl in time spans declined and urban development tended to be compact.