CsI:Gd crystal was grown by the Bridgeman method and its scintillation properties were investigated. The wavelength peak of the luminescence spectrum for the crystal excited by X-ray was 419 nm. The range of the spectrum was from 300 nm to 800 nm. The spectrum well matched to the quantum efficiency of a typical bi-alkali photo-multiplier tube(PMT). An energy resolution of 48.2 % was obtained for 662 keV ${gamma}$-rays of $^{137}Cs$. The three decay times were obtained as a fast(557.4 ns, 42.2 %), intermediate (1.78 ${mu}s$, 29.7 %) and slow (5.43 ${mu}s$, 28.1 %) components, respectively.