In this work, STM measurements are employed to study the growth behaviors of alumina formed on the NiAl(110) surface under low coverage of oxygen dose (3 Langmuir and 120 Langmuir). Utilizing the capability of STM, the surface structures and the corresponding electronic properties of these alumina can be probed, respectively. The alumina nanoclusters are observed at sample bias 4V after the NiAl(110) surface is oxidized. However, when the bias is lower to 2V, the electronic states of the oxide are not accessible, so that the electrons can only tunnel between the tip and the metal support. In this case, the oxide just modulates the potential barrier as a function of position. Compared with the topographic image of the alumina formed by 3L and 120L oxygen dose, the growing behavior of the alumina/NiAl(110) at the initial stage could be measured.