Article 98 of civil procedur of Iran has allowed the claimant to change the mode of claim, before the end of the first sitting of the court. Lawyers and writers of Civil Procedure have cosidered no more to the concept of change mode of claim and its procedure. Also law pointed out to change mode of claim ambiguously and didn’t explain that “what the change mode of claim is and how its procedure is”. The judicial precedent didn’t fill this gap and didn’t get clear precedent for changing the mode of claim. This study determins changing the mode of claim and its procedure through a comparative study of legal system of France and Iran. For this purpose, we first study the change mode of claim briefly, and then we check out the component of claim (action); also we consider concept of changing the mode of claim and compare it with parallel cases, and afterwards we will study the procedure of changing the mode of claim, and finally the coclusion of research will be mentioned briefly.