TB1301 as a new chem. entity of the anti-chronic myeloid leukemia (CML), is a kind of imatinib me-better drugs.Objective: Exptl. study on acute toxicity of TB1301 in Kunming mice.Methods: The acute toxicity of TB1301 was studied in Kunming mice with LD 50% method (LD50).General status was measured to evaluate the toxicity.Conclusion: TB1301 LD50 (i. g) was 766.61 mg/kg with its 95% confidence interval of 537.25∼949.49 mg/kg.TB1301 LD50 (i. v) was 118.20 mg/kg with its 95% confidence interval of 94.42∼140.08 mg/kg.