The acute toxicity of povidone iodine, trichloroisocyanuric acid, and lambda-cyhalothrin on Cyprinus carpio Songhe [(118.8±5.63) cm in length, (72.75±15.11) g in body mass]was investigated at a water temperature of (20±1) ℃ using a static bioassay method. The results revealed that the median lethal concentration (LC₅₀) of povidone iodine was 870.551 mg/L at 24 h, 790.650 mg/L at 48 h, 694.959 mg/L at 72 h, and 654.692 mg/L at 96 h, with a safe concentration of 195.653 mg/L. For trichloroisocyanuric acid, the LC₅₀ was 23.076 mg/L at 24 h, 19.608 mg/L at 48 h, 15.674 mg/L at 72 h, and 13.871 mg/L at 96 h, with a safe concentration of 4.247 mg/L. The LC₅₀ of lambda-cyhalothrin was 4.620 mg/L at 24 h, 2.216 mg/L at 48 h, 1.205 mg/L at 72 h, and 0.847 mg/L at 96 h, with a safe concentration of 0.153 mg/L. The descending order of toxicity among the three substances to C.carpio Songhe was lambda-cyhalothrin > trichloroisocyanuric acid > povidone iodine. Based on toxicity evaluation criteria, povidone iodine and trichloroisocyanuric acid exhibited low toxicity for C.carpio Songhe and could be considered as the preferred choices in practical applications. However, lambda-cyhalothrin demonstrated high toxicity for C.carpio Songhe, requiring careful consideration and cautious use in practice.