Objective] To study the toxicity of HCFC 225 and its security. [Methods] To confirm acute toxicity grade by acute toxicity test in experiment animal. To find out the target organ and the concentrations for testing subacute toxicity by a 28 day repeated inhalation exposure. [Results] Acute peroral LD 50 for female mice is 20 g/kg,for male mice is 14 7 g/kg.Acute inhalation LC 50 for mice is 526 670 mg/m 3.Acute peroral LD 50 for rats is more than 21 5 g/kg. The result of day 28 repeated inhalation study in rats showed that the main target organs after inhalation of HCFC 225 were lung,liver and then kidney. Toxicity was shown that the serum ALT,AST,CR and BUN increased;gore,bleeding and infiltration of phlogostic cells;and pathologic changes such as light cloudy swelling and aquosity. The Lowest Observed Effect Concentration(LOEC) is 37 350 mg/m 3. The No Observed Effect Concentration (NOEC) is 12 450 mg/m 3. [Conclusion] HCFC 225 belongs to slight toxicity grade. The result of 28 day repeated inhalation study in rats shows the main target organs after inhalation of HCFC 225 are lung,liver and then kidney. LOEC is 37 350 mg/m 3. NOEC is 12 450 mg/m 3.