In this presentation, graphene nanoelectromechanical (NEM) resonator based ultra-sensitive mass detection will be demonstrated. The amount of mass loaded on the graphene NEM resonator can be measured by resonant frequency shifts. The sensitivity of frequency change detection by mass loading could be improved by optimizing device structure and reducing effective mass of graphene. Our newly developed concept of utilizing the non-linear behavior of graphene resonator will be introduced for improving the resolution of frequency change detection, which is directly related to the resolution of mass change detection. A single molecule protein sequencing will be suggested for one of the promising applications of our devices will be introduced at the end of presentation.