Urbanisation in China has developed dramatically in recent years.With insufficient domestic demands，however，the transition in the mode of economy development faces challenges.Other than using the framework of income-consumption，this paper attempts to adopt the perspective of social structure and proposes to drive consumption through expanding the middle class.This perspective is helpful for improving the efficiency of social policies and also gives full play to market mechanism in terms of optimizing resources.It is found from the empirical analysis that the middle class has the strongest purchasing power and consumer desires and thus is the main driver in increasing consumption.The marginal middle class，mainly consisting of skilled migrant workers，lower white collars and unemployed university graduates or those with lower income，also exhibits substantial consumer aspirations and needs，especially in consumption of houses and leisure services，and therefore also plays important roles in the process of stimulating consumption.Policy advices emphasize enhancing the purchasing power of the middle class and the social welfare system and also increasing life chances of the marginal middle class.