Abstract: Experiments were conducted with red cowpea(Vigna ungniculata ssp.sesquipedalis cv.chuangfeng) as experimental materials to study the numbers,activity and responsiveness of root border cells to Al stress using aeroponic culture.The results indicated that root border cell number of red cowpea increased rapidly with the elongation of root.It reached peak being around 5300 when roots were 10mm,then it decreased slightly and kept rather stable.All root border cells had a high viability,which was higher than 85%.With the extending of root,activities of board cell were promoted stepwise;while peetin methylestcrase(PME) activity in root cap was abated indicating that PME activities were closely related with root border cell separation.Root border cell's viability in intro decreased with increasing of concentration of Al3+ and/or their access time to Al3+.No significant difference on PME activities in root cap was observed between treatments treated under different Al3+ concentration when cowpea roots had same length.