Lab. of Accelerator Development(LAD) in Korea Institute of Radiological & Medical Sciences(KIRAMS) developed a 13MeV medical cyclotron, named by KIRAMS-13, for Positron Emission Tomography(PET) in 2001. Now, KIRAMS-13 has spread to the provinces through the national project, “Development of Cyclotron and FDG Synthesis modules.” But, there is just one cyclotron for Single Photon Emission Computed Tomography(SPECT) in Korea, which is made by IBA, Belgium. If any problem is happened, we should shut off the cyclotron until an engineer fixes them. So, we decide to develop a 30MeV cyclotron, named KIRAMS-30, which has high-performance compared with existing commercial cyclotrons and will install this machine to radioactive isotopes production and research in Advanced Radiation Technology Institute(ARTI). In this paper, we design a RF system, such as cavity, power coupler, and so on. At design of RF components, we consider mechanical stability, RF heating and cooling, arcing and low maintenance. We simulate the RF system of KIRAS-30 with CST Microwave Studio(MWS) and present simulation results.