To observe the effect of Shen Yuan Dan(SYD) on 5-HT in the serum of Sprague-Dawley (SD) rats with acute myocardial infarction(AMI)/depression,and study the mechanisms of the theory Enhancing-qi in Removing-stasis in treating AMI/depression.Methods:Thirty SD rats were allocated into normal group,model group,H-SYD(high dose SYD) group,L-SYD(Low dose SYD) group and control group randomly.The model was estabished by coronary artery ligation with chronic mild unpredictable stimulation and fed alone.Models were given high dose of SYD,low dose of SYD,fluoxetine and distilled water.All the models were put into death 3 days later.The levels of 5-HT and TNF-α in rats serum of different groups were measured.Results:1) Serum 5-HT concentration.Compared with the normal group,5-HT concentration in the model group significantly decreased (P<0.05); The serum concentration of 5-HT between the SYD group was significantly higher than that of the model group (P<0.05).The concentration of 5-HT in serum of SYD group and control group had no statistical difference (P>0.05).2) Serum TNF-α concentration.Compared with the normal group,the serum TNF-α concentration in the model group has no statistical difference (P>0.05),besides,TNF-α in serum of L-SYD group was higher than those of the normal group,control group and H-SYD group but without any significant difference(P>0.05).Conclusion:SYD can reduce the level of 5-HT in serum but failed to affect TNF-α level.