Abstract: With the increase of urban population mobility in modern China， it is necessary to discuss in depth the changes in the operational mode of social relations that are based on the different patterns of association. During the period of the Republic of China， Beijing and Tianjin were the biggest cities in northern China， and the scale of population movement was large， resulting in fewer blood related relatives than strangers and outsiders in social relations among the people. At the same time， under the influence of Manchus’ lifestyle， the urban culture of Beijing and Tianjin still attached great importance to the ritual gradation based on blood relation， manifested in stipulating everyone’s status and behavior standards in accordance with blood relation ethics. By analyzing funeral crosswalks (Xiangsheng) that reflected the urban culture of Beijing and Tianjin of the period， this paper argues that due to the dominant presence of migrant population， the pressure of family opinions gave way to the more tolerant community public opinions. Facing the shortage of blood relatives to carry out the normative procedure of ritual gradation， people began to embrace outsiders and strangers into the core circle of differentiated association of their mourning system. In this process， the operational logic of social relationship relied on “the distinction between righteousness and gains”， reflected as “friendship” and “taking advantage”. In the absence of blood relatives， the“friendship” based on“righteousness” enabled outsiders and strangers to enter the core circle of the differential mode of association， while “taking advantage” meant not only the pursuit of self-interest， but also the process where in the outsiders and strangers could adjust their positions appropriate to the differential mode of association.

Key words: the operation mode of social relations, urban culture of Beijing and Tianjin in Republic of China, funeral Xiangsheng, the differential mode of association