At the period of the tenth five-year-planning, the progress of urbanization in our country will get into a new stage. The status quo of rural towns distributed everywhere will be changed completely. The emphases of urbanization will turn steps to improving the quality of urbanization instead of increasing the quantity of towns. And the development of major towns will be a vital link of urbanization at the period of the tenth five-year-planning. Ningbo city, locating at the south of the urban zone of Changjiang River Delta, is an important component of the urban zone. At present, Ningbo city has developed a four-type urban and town system which includes key city, vice-key city, major town and common town and the Ningbo key city is its center. However, the Ningbo city's urban and town system is suffering from a lot of problems, such as the asymmetry of urban and town's spatial distribution, the unprominence of functional structure's arrangement and the irrationality of size-distributed order which have influenced the sustainable development of urbanization. The paper is mainly about the development of major town in Ningbo city's urban and town system. At first, from analyzing region background and current situation of major towns in Ningbo city's urban and town system, the paper studies the factors of motility and restriction that affect the development of major town. Second, major town has lots of regional advantages and rational economic structure. It can accept the radiation of key urban and vice-key urban. Then it will promote the development of country. The goals of developing major town are to accelerate the progress of rural urbanization. The third, the paper mainly studies concentrated motility and restriction mechanism of major towns. The studies on constructing major town and giving free rein to the functions of major town at the progress of urbanization are very important. We should pursue and perfect the rule of major town uninterrupted in the future.