The present research tries to study the principle of innocence in the preliminary stage of investigation, that is, after the discovery of crime and before the procedure of judgment. In fact, the preliminary investigations and legal actions. Are of high importance. Regarding the subject, aim, feature and involving parties, the criminal procedure is different form legal procedure and these differences have made it important and sensitive as one of the critical stages of criminal procedure. At this stage, the culprit who is deemed to be innocent up the time his charge is not proven, in the light of the said principle, has some legal rights and this matter should be taken into consideration. In the other words, since this principle claims that the culprit is innocent until his charge is not proven, he should not be forced to confess or testify against himself, thus he must not impel to answer for the claims against him and he has the right to keep silence. He may have a lawyer or an interpreter and take advantages of his assistance to prove his own innocence. Further more, for the other benefits of the said principle, he is of individual freedom during the preliminary investigations and his arrest, for the benefits of social interests, is confined to exceptional cases together with special circumstances.The above benefits are examined with regard to international documents, the European human rights convention, American human rights convention, the international civil and political agreement, international criminal charter and Iranian legal system.