Mechanical resonance properties of porous graphene resonators were investigated by simulation studies. The finite element method was utilized to design the porous graphene membrane pattern and to calculate the mechanical resonance frequency and quality factor. The changes in the resonance frequency and quality factor were systematically studied by changing the size, number, and relative location of pores on the graphene membrane. Mass loss and carbon-carbon bond break were found to be the main competing parameters for determining its mechanical resonance properties. The correlation between the geometry and the damping effect on the mechanical resonance of graphene was considered by suggesting a model on the damping factor and by calculating the membrane deflections according to the pore location. Based on the simulation results, an optimal porosity and porous geometry were found that gives the maximum resonance frequency and quality factor. Suspended graphene with various number pore structures was experimentally realized, and their mechanical resonance behaviors were measured. The trend of changes in resonance frequency and quality factor according to the number of pores in the experiment was qualitatively agreed with simulation results.