The GSO scintillator has a very excellent radiation resistance, fast decay time and large amounts of light yield. Because of these features, GSO will be used to upgrade the current LHCf detector. We examined the features of GSO by using heavy ion beam at Heavy Ion Medical Accelerator in Chiba (HIMAC) Japan. The linearity of PMT R7400 for the large light yield of GSO with a 132Xe beam and the radiation hardness with a 12C beam were measured. As a result, GSO scintillator showed a good linearity up to the signal corresponding to 6 TeV EM-shower maximum in the LHCf detector, and a good radiation hardness up to 7×105Gy. For the LHCf Arm1 detector, small scaled GSO crystals (GSO bars), have been fabricated for the position determination detector. 5 GSO bars have been manufactured and its performance have been evaluated using 12C beam. Its light yield and position dependency have been evaluated.