Laser-induced fluorescence excitation spectrum of B2Σ＋— X2Σ+ transition of gas-phase AlO radical cooled in a supe rsonic jet has been observed in the range of 430—480nm.AlO was produced by reac ting O2 with Al atoms from a dc discharge-sputtering source.The obser ved vibrational bands were identified as V′-V″=1,2,3 transitions respectively. The vibrational frequencies and anharmonic constants were obtained for both the ground state X2Σ+ and the excited state B2Σ+.Furthermore a rotational analysis of the (1,4) band was made.The abno rmal intensity of the V″=5 transitions is discussed.