Human need is the motive power of social development. It is the object's function to satisfy human needs. Though the object's structure is the major reason to determine its function to a great extent, as to meeting human needs, function is more important than structure, because of human's subjective initiatives to create and to choose. Under most circumstances, it's wrong to declare only a particular structure can meet the needs, for there are other structures that can be the substitutions. Therefore, no social structure or system is so sacrosanct that it cannot be changed. The structure of socialism should also be determined by the socialist function. The advantage of socialism comes neither from any calculation formula nor fixed structures of human society, but its function to resolve serious problems in capitalist system, such as class polarization, economical crisis, etc. If one socialist structure can't make this, people may cast it away and seek another one. Thus, the function of socialism is clear while the structure of socialism can be different in different countries and under different conditions.  The classic writers of Marxism have expounded socialism on both its structures and functions. However, they pay more and more attention to socialist structures while less and less to its functions with the change of socialism from theory to practice. Excessive stresses on structure and its solidification in reality bring up much trouble to social development, until Deng Xiaoping points out socialist functions with special emphasis unprecedentedly，which lay a foundation for China's Reform and Opening Up policy. According to his theory of socialist essence，the function of common prosperity is the most important thing to socialism, while the structure of ownership is only the means to achieve it. Such theory helps those people who regard a particular structure as socialism itself to change their mind.  To achieve socialist function of common prosperity in the primary stage of socialism, the government, on behalf of the whole society's interest, must discard the wrong perception on socialism and reform the national governance system. First, the proportion of different ownerships should be adjusted much more flexible according to the actual demands, which will help those market participants to compete equally and fully to bring more productivity. At the same time, the gap of wealth must be controlled in the acceptable range to the public by means of redistribution and social insurance system. It is achieving common prosperity that can bring political stability and social harmony. Second, the government must fight legally and effectively against those anti-market factors, such as corruption, monopoly and heredity which lead to polarizations between the rich and the poor. Democracy, constitutionalism and republicanism may originate from the West, but are not exclusive to the West. Without the rule of the people and the rule by law, problems like rent-seeking and autocracy may never be solved. In modern times, the legitimacy of political power is mainly based on the people's authorization but not on the control of economy and culture. Authoritarian regimes throughout history always spare no effort to control social wealth and ideology, but can never prevent them from being overturned.