Banana oligosaccharides (BOS) were extracted with water, and then separated and purified using column chromatography. Gel penetration chromatography was used to determine the molecular weights. Thin layer chromatogram and capillary electrophoresis were employed to analyze the monosaccharide composition. The indican bond and structure of the BOS molecule were determined using Fourier transform infrared spectroscopy and nuclear magnetic resonance. Results showed that BOS were probably composed of eight β-D-pyran glucose units linked with 1→6 indican bonds. The laxative effects of BOS were investigated in mice using the method described in "Handbook of Technical Standards for Testing and Assessment of Health Food in China." The length of the small intestine over which a carbon suspension solution advanced in mice treated with low-, middle-, and high-dose BOS was significantly greater than that in the model group, suggesting that BOS are effective in accelerating the movement of the small intestine.