Background. Tai Chi is effective in preventing heart disease (CHD) risk, but the molecular mechanism remains unclear. Mitogen-activated protein kinase (MAPK) signaling plays a critical role in the pathogenesis of CHD and can be activated by miR-126. Tai Chi may exert its protective function through the miR-126-modulated MAPK pathway. Methods. The CHD patients after PCI were randomized into the CG group (CG) (n = 19, normal care) and Tai Chi group (TG) (Tai Chi intervention, n = 17). Epicardial adipose tissue volume (EATV) (one main adverse cardiovascular event of CHD), HR (heart rate), QoL (quality of life) scores, and balance performance were measured in the two groups. The body fat content, abdominal subcutaneous fat, and visceral fat were measured to reflect the improvement of adipose tissue dysfunction. The levels of miR-126 and MAPK-associated molecules were measured in peripheral blood leukocytes. Meanwhile, the effects of miR-126 silence and mimic on MAPK-associated molecules were also explored in cardiac cell H9C2. Results. After the 3-month intervention, Tai Chi reduced EATV and HR and increased QoL scores and balance performance, respectively (P<0.05). The fat percentage, body fat mass, and BMI were also significantly reduced after Tai Chi intervention (P<0.05). The levels of miR-126, MAPK, JNK, and ERK in the TG group were lower than those in the CG group (P<0.05). The miR-126 levels had a strong relationship with the values of EATV, HR, and QoL scores (P<0.05). miR-126 silence or mimic inactivated or activated MAPK-associated molecules in the cardiac cell lines. Conclusions. Tai Chi improved CHD risk by inactivating the MAPK/ERK pathway via serum miR-126.