This article has analyzed principle no.8 of the Constitution from three aspects: 1-verbal analysis 2-conceptual analysis 3-ways to execute this principle. In first section a precise definition of "call to good", "good and evil" (both in law and in jurisprudence) and "government" have been presented. In second section to have a better understanding of principle no.8, issues such as the relation between "enjoining good" and supervision, fields of enjoining good and forbidding the evil, public supervision as an obligation, generality of who enjoin good and forbid the evil, generality of whom are called to good and are forbidden from the evil, generality of instances of commanding and forbidding and tools of public supervision over the government have been discussed. Third section takes a brief look at contents of this principle and suggests that parliament should ratify the establishment of a coordinating organization as a necessary step to execute principle no.8; an organization which is in charge of policymaking, planning and supervising accurate execution of enjoining good and forbidding the evil in society.