This paper is structured as follows: Section 2 overviews the security of Andriod and iOS. Section 3 introduces the security models of them (Android and iOS) and discusses different views for each OS and the applied mechanisms in them. Section 4 reviews the threats and malw ares of them. In section 5 we compare iOS against Android based on set of references and some concluded measures. We study the comparison criteria and measurements to give a sight about strengths and weaknesses for the intended OSs. Finally, discussion and conclusions are presented.