Abstract: In order to study the effect of different alkali on the structure of cassava starch,the cassava starch was treated with alkali/alcohol solutions prepared from IA main group alkali metal hydroxide. The treated cassava starches were characterized by polarized light microscopy,laser confocal microscopy,scanning electron microscopy,X-ray diffraction analysis,fourier transform infrared spectroscopy. The amylose contents and reducing sugar contents of the samples were detected. The results showed that,the integrity of cassava starches particle morphology was not impacted as treated with different alkali/alcohol solutions. The result of fourier transform infrared spectroscopy showed that no new functional group formed,but the peak at 3412 cm^-1 of treated cassava starches shifted to the high wavenumber and its intensity was lower than the native cassava starch. Moreover,as the period of the corresponding element of the alkali metal increased,the destruction of the internal structure of starch was obviously enhanced. The crystal form of cassava starches were changed and its relative crystallinity decreased from 22.03% to 15.07%. The amylose contents of the cassava starches was gradually decreased from 22.30% to 16.51%.The total reducing sugar contents of all treated samples was higher than the native cassava starch. In summary,the effect of different alkali/alcohol solution treatments on the structure of cassava starch showed significant differences.