Colchicine under concentration of 0,0.1,0.2,0.5,1.0 and 2.0 g/L and garlic root tip were cultured 12,24,36,48 and 60 h separately，the effect of morphological changes of garlic root tip induced by different concentrations of colchicine at different periods were studied.The results showed that under 0.5 g/L treatment dealing with from 24 to 48 hours，the expansion rate was more than 82%，the comprehensive effect was better.