A virtual machine (VM) has access onl y a portion of computer resources but that appears to be a whole computer.Virtual machines are running on the same computer system hardware. The performance of the virtual machines are depends on the performance of the host operating s y stem on which the y are running. In this work the performance of different guest VM's on the same host operating s y stem has been anal y zed. For this experimentation Ubuntu (Linux based operating s y stem) is used as host operating s y stem and Ubuntu as well as CentOS operating s y stems are used as guest operating s y stem.Performance measurement of the virtual machines is done in the same conditions for both guest operating s y stems using different benchmark. In this work the performance of different guest VM has been anal y zed using S y sBench on CPU performance, Mutual Exclusion, Threads and Online Transaction Processing Test performance parameters. Results shows that for CPU Performance and mutex, CentOS 6.3 gives better results and for OLTP and Threads performance test Ubuntu performs well.