In X-ray computed tomography (CT), variability in tube voltage and current setting may affect the image quality. Based on an industrial X-ray micro-CT scanner, this paper will investigate the impact of the X-ray tube setting on image quality of the projection images as well as the reconstruction results with various voltage and current choices in the CT experiments. Fresh corn is initially selected as an experimental sample in 6 different series of measurements. We set the tube current at 130μA, 200μA, 270μA while keeping the tube voltage and other acquisition parameters constant, and then keep the tube current constant while varying the tube voltage at 70kV and 100kV, respectively. For evaluation both the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) are calculated as image quality criteria for each set of the projected images and reconstructed images. The results indicate that increasing the tube current and voltage can both improve the SNR and CNR. Furthermore, the tube voltage has more impact on the improvements. At the same time, the variations on image quality of reconstruction images keeps the same pace with that of the projection images. The reliability of the conclusion will be further explored experimentally using aircraft blades in CT nondestructive testing.