A survey conducted in 2000 about the social network of residents in Beijing found that the sequential order of the member list of one’s personal social network issued by interviewees themselves co-relates with the density of one’s social network，the frequency of social interaction，and the range of significant issues in which the interviewee would consider to involve a specific partner. The more intimate and the longer the relationship is and the higher the frequency of their social interaction，the more likely a specific partner to be put on top of the list. Meanwhile，the higher the position of a partner on the list，the more likely he or she would be considered by the interviewee as a suitable interlocutor for a wider range of significant issues. As we go down from the top to the bottom of the list，the instrumental contents of social interaction tend to increase while the affectional contents decrease. To a large extent，these findings prove the validity of“the differential mode of association”thesis proposed by Fei Xiaotong half a century ago. Moreover，they also illustrate that“the differential mode of association” appears not only in social networks based on instrumental relationship but also in those based on mixed relationship，i.e. a combination of instrumental，affectional，and social interaction，which could well be considered as a modern extension of“the differential mode of association”thesis. In fact，as Fei Xiaotong has observed himself，“the differential mode of association” in traditional Chinese society is a unity of instrumentality and moral obligation. The fact that interviewees tend to put one’s family members and closely connected kinsfolk on the top of the list might be seen as a reflection of the stronger bond of moral obligations between them.