Macau is a rather safe city in the sense that the crime rates are relatively low. This paper is trying to point out that informal social control play an essential role in the safety of the city. Social bonds are very important for the building of informal social control, and it is discussed that individuals with homogenous culture living in this small place are intricately connected with each other. A lot of scholars think that informal social control takes effect when individuals monitor and prevent others from having socially undesirable behaviors. However, in this paper, informal social control are not treated as something merely external to individuals. It is also internal, and more powerful, when it enables people to internalize the moral norms. A lot of theories, including social disorganization theory, social bond theory, etc., are applied in this paper. In addition, some literary works are also covered for discussion and analysis. Although this is not an empirical study, it tries to give a theoretical perspective on the phenomena.