Chosen hemerocallis and cut chrysanthemum seedlings as materials，mercuric chloride at the rate of 0.005,0.010,0.030,0.050 and 0.070 mg/L was added into culture medium,respectively,the effects of mercuric chloride on the pollution prevention of tissue culture seedling were studied.The results showed that mercuric chloride could significantly eliminate pollution at 0.010 mg/L concentration by 2 to 3 switches.As mercuric chloride contents were between 0.030 and 0.070 mg/L，the pollution was markedly inhibited and a positive relationship was found between inhibition effect and concentrations.0.080 mg/L mercuric chloride was unfavorable for tissue culture seedlings indicted by leaf chlorosis and plant death.It was concluded that concentrations between 0.030 and 0.070 mg/L may be the better choice to prevent pollution for hemerocallis and cut chrysanthemum seedlings.