We measured temperature dependence of α/γ-ratio of three sample pieces of Ce 0.5 mol% doped Gd2SiO5 crystalline scintillator, which are cut from different ingots and have a dimension of 24 × 24 × 5 mm3. The temperature is controlled by a heat bath within ±0.5 K at + 20, 0, and -20 degrees of Celcius. By using intrinsic activity of 152Gd 2.14 MeV α-ray, it is irradiated uniformly inside the scintillator. To determine α/γ-ratio precisely, we measured input energy and pulse height linearity between 60 keV and 511 keV, at three temperature conditions. Then, we measure the α-ray response of the scintillator by a passive rejection any outer backgrounds by Pb and Sn blocks. As a result, α/γ-ratio of 0.5 mol% Ce doped GSO is turned out to be ∼ 0.175, and it showed a gradual temperature dependence of ∼ 0.4 keV/K.