l-arabinose was prepared from corncob by the method of acid hydrolysis. Components in the hydrolyzate of corncob were analysed by the methods of HPLC, TLC and High-efficient thin layer chromatography scanning analysis. Effect of each factor on l-arabinose’s preparing was investigated. Relative amount of each component in the hydrolyzate can be obtained. The optimum conditions for l-arabinose’s preparing were obtained by conducting orthogonal experiment.