The invention belonging to the cell biology and pharmacology technical field relates to the purpose of a Chinese traditional medicine monomeric compound, in particularly to the new purpose of a protocatechuic acid in the aspect of promoting the external proliferation and induction-differentiation of a nerve stem cell. The invention is characterized in the application of producing medicine to treat the neurodegenerative diseases by nerve stem cell transplantation, in the application of producing neurenergen and cell differential agent for restoring damaged nerve tissues and reconstructing nerve functions, and in the application of constructing high efficient medical screening model to initially screen and appraise the efficacy of medicine. The invention confirms the new phamacoloic activity of the protocatechuic acid, providing material basis with regard to prevention effect of the Chinese traditional medicine, and providing reference for the development of new medicine with independent intellectual property rights.