Based on the related theories about core meaning of compact city both athome and abroad, the paper constructs the appraisal index system of the synthesis level of the city compactness embarking economic compactness, land compactness, population compactness and traffic compactness. With the method of entropy, the paper researched the comprehensive city compactness of Wuhu in 1996，2005 and 2009.The results showed that the compact index score in 1996 were up compared to 2005.In addition to economic compactness index rose to 2009，other indicators have come down. The main factors affecting the Wuhu city compact changes：Metro construction and zoning adjustment，Development Zone，the construction and development of urban transport organization，population size，land use planning and policy guidance.