The most important issue in a high intensity proton accelerator is to keep the accelerator tunnel in a hands-on-maintenance condition. A collimation system was designed and installed in 3GeV Rapid Cycling Synchrotron (RCS) at the Japan Proton Accelerator Research Complex (J-PARC) to be localized the beam loss point to a restricted area. The experimental results indicated that the RCS collimation system performs well enough such that nearly all the ring components are maintained in good condition. However, as the beam power increased, unexpected losses downstream of the injection foil increased. Therefore, an additional collimator was installed that successfully reduced such unexpected losses.