Abstract: This paper studies the Urban system in Yantze delta using fractal theory. We figures out the primate city index in Yantze delta according to the town primacy rule of M.Jefferson, and then the town-size fractal dimension is worked out to discuss to the scale structure of the urban system in Yantze delta. In addition, spatial correlation dimension of the town-size distribution in Yantze delta is put forward to analyses the spatial structure of urban system. According to all these analyses it points out there are some deficiencies of the urban system in Yangtze delta, such as:(1)The scale distributing in Yangtze delta is primacy distributing; (2) Middle-small cities develop much slower than big cities; (3) The capacity of spatial interaction isn’t strong enough. The paper puts forward the direction for developing the urban system in Yangtze delta: Realize the integration of regional economy, and speed up the development in Yangtzi delta.