Background One of the misbehavior in Research Ethics is Plagiarism that it means to appropriate other' work as one's own. Self-Plagiarism is a kind of plagiarism. In this paper I will deal with these questions: what is plagiarism and what kinds does it have? Is the concept of self-plagiarism reasonable? Conclusion Self-plagiarism is republishing the whole or main parts of a work، without appropriate citation to pervious publication. Duplicate publication، salami publication and Text recycling are kinds of self-plagiarism. Because of the impossibility of theft of own self، It is suggested to use duplicate publication instead of self-plagiarism. Some of the results of this paper are: the researchers and authors are obligated to inform appropriately using of their former published works in their new writings to readers and editors of journals; if they want to produce several papers from one research such as Ph. D. thesis that they have overlap، they have to inform that to editors; they have to avoid republish the paper has been published in a conference before.