Wenxin Decoction is an effective prescription for unstable angina pectoris after coronary heart disease. The aim of this study was to observe the acute toxicity of the decoction to evaluate its safety. Methods: The maximum administration volume(5.2 g/mL) and the maximum drug concentration (0.7 mL/20 g each time) were administered to mice by three hours in 24 hours and 2 weeks respectively. The appearance, behavior, general state, respiration, toxic reaction and death status of the experimental mice were recorded in detail. The body weight and feeding rate of the surviving mice were also recorded every day. Liver function was examined by blood test after the treatment. Results: No significant acute toxicity reaction was observed 3 times in 1 days in the experimental mice with the maximum dose 425 g/kg. And no abnormality was found in liver and kidney function examine. Conclusion: Wenxin decoction is relatively safe.