Abstract: In order to screen efficient fungicides with low toxicity that can prevent and control root rot of tobacco seedlings caused by Aphanomyces iridis, the toxicities of 70% thiophanate-methyl wettable powder(WP), 58% metalaxyl-mancozeb wettable powder(WP), 50% chlorobromo isocyanuric acid soluble powder(SP), 20% cinnamamide hydrochloride solution(AS), 30% propamocarb-azoxystrobin suspension concentrate (SC), 80% enoylmorpholine water dispersible granules (WG), and 48% propamocarb-cupric-ammonium solution(AS)against A.iridis were tested by the mycelial growth rate method. Simultaneously, control efficacy and safety were evaluated by inoculation into floating seedlings. The results showed that 48% propamocarb-cupric-ammonium solution and 30% propamocarb- azoxystrobin had the strongest inhibitory efficacy against the mycelium of A.iridis with EC₅₀ values of 0.255 and 0.367 μg/mL, respectively. This was followed by 20% cinnamamide hydrochloride and 58% metalaxyl-mancozeb with EC₅₀ values of 14.107 and 37.495 μg/mL, respectively. The antifungal effect of 70% thiophanate-methyl was the worst. The result of inoculation experiment showed that 48% propamocarb-cupric-ammonium solution and 30% propamocarb-azoxystrobin had a good control efficacy on root rot of tobacco seedlings caused by A.iridis with control efficacy ranging from 86.88% to 94.61%, and the treatment of 30% propamocarb-azoxystrobin had good safety for tobacco seedlings. The control efficacy of 58% metalaxyl-mancozeb was poor, being less than 30%.