【Abstract】 Objective To study the mechanism and the relationship of the follistatinlike protein 1 and miRNA200 in acute myocardial infarction (AMI) in rats. Methods 20 SD rats were divided into AMI group and Sham group. AMI group was operated with the left anterior descending coronary artery ligation, and Sham group was not ligated. Venous blood and heart tissue were collected postoperative 1d, plasma cTnI and FSTL1 expression were tested by ELISA. The plasma and heart rnomiR200b3p were detected by qRTPC, and FSTL1 protein levels were performed by Western blot. Results The plasma FSTL1 expression of AMI group were increased significantly compared with that of Sham group (P＜005). The AUC was 1000 (P＜005). mRNA level and protein level of FSTL1 of AMI group were significantly lower in that of Sham group (P＜005) at postoperative 1d. The plasma rnomiR200b3p expression in AMI group was significantly decreased compared with that in Sham group (P＜005). The heart tissue rnomiR200b3p expression in AMI rats were significantly increased compared with that in Sham group (P＜005). Conclusion FSTL1 and rnomiR200b3p may be associated with AMI, and FSTL1 can be used as a biomarker of myocardial injury, and rnomiR200b3p may involve in inflammation, oxidative stress and cell apoptosis in AMI by mediated FSTL1.