Abstract: In order to utilize efficiently protein resource in discarded tobacco leaf, the optimum technological conditions for extracting protein from discarded tobacco leaf by the method of dissolving with alkali and depositing with acid were investigated. Moreover, amino acid composition of the protein was analyzed by HPLC system. The results showed that optimum extracting conditions for tobacco leaf grinding were: the 1∶17 ratio of tobacco leaf/water, 60℃, pH8.0 and twice grinding. Optimum extracting conditions for protein were: 60℃, pH8.0, 60 min and extracting for three times with agitation. Optimum conditions for acid depositing protein were: pH3.0, 4℃ for 8 h and the extraction rate reached 86.71% under the conditions. The obtained protein obtained contained relatively complete amino acid composition, and was rich in essential amino acids. In addition, higher amino acid score was found in the protein obtained according to the process mentioned above. It indicated that tobacco leaf protein was a kind of valuable resource.