The French philosopher Michel Foucault believes that discourse is in essence the force exerted on things. In the discourse theory, this kind of power is the vehicle that grants verbal communication structure—“illocutionary force”, which makes the compulsoriness of legal discourse possible and at the same time imposes constraints on it. By introducing the concept of “illocutionary force” from classic discourse theory, the compulsory relationship between the orator and the audience in legal discourse has been revealed.To put it clearly, the relationship consists of external compulsoriness and internal compulsoriness, the former of which can be divided into three categories:“prohibition”,“distinction” and “acknowledgement” and the later encompasses “commentary”,“signature” and “paradigm”.