With the root tip as experimental materials,toxic effect of sodium chloride on Allium cepa var.aggreatum root tip was investigated.The Allium cepa var.aggreatum root tip cells were exposed to aqueous solution of sodium chloride with different concentration（0.05,0.1,0.2,0.3 mol/L） for 12 h,24 h and 48 h,respectively.And then the mitotic index,micronucleus rate and chromosome aberration of the Allium cepa var.aggreatum root tip cell were investigated.The experimental results indicated that with the elevated concentrations of sodium chloride aqueous and the increase of exposing time,the mitotic index decreased,chromosome aberration rate and micronucleus rate increased gradually.Moreover,the maximum value was reached when the concentration of sodium chloride aqueous was 0.3 mol/L and the exposure time was 48 h,which indicated that sodium chloride is a kind of stress factor.