Mobile computing is considered as low-cost computing systems. Now days it dominates almost every aspects of our lives from mobile banking to mobile purchasing to mobile browsing, etc. As the demands of mobile phone increase in our lives, making the system secure from authorized access, malicious threads etc is very important. In mobile computing one of the most important need is Mobile security or mobile phone security. Operating system plays an important role to gain both functionalities and quality (e.g., security) of a system. This paper briefly discuss both the operating systems in terms of security .Also this paper surveys the software architecture of two of the leading mobile operating systems such as Android (Linux), and Windows Mobile. Furthermore, at the end the result of survey we have conducted have been proved that Android is providing better security measures than Windows8