Abstract: Objective To explore the treatment of percutaneous coronary intervention (PCI) , and to comparatively study on the protection of side support by using the active and passive expansion technique.Method 78 patients with coronary artery disease were protected by using balloon technique, there were two groups: the active expansion group (n=41) and the side support balloon (n=37) , the TIMI classification、myocardial perfusion rating (MBG) , TIMI myocardial perfusion rating (TMP) and the incidence of marginal vascular interlayer were observed and analyzed. Results After the main support was put in, the proportion of patients with side branches of TIMI、 MBG and TMP was at level 3 and the proportion of patients with active balloon expansion was 93%, the margin expansion group was 84%, the difference was not statistically significant (P>0.05) ; the incidence of intersecting vascular interlayer in active dilatation group was 24%, the margin expansion group was 8%, and there were statistical differences (P<0.05) . Conclusions Using the technique of holding balloon to protect the side branches, both the active expansion of the side support balloon and the expansion of the side support balloon can significantly reduce the risk of the main stent placement in the posterior branch of the blood vessel, however the incidence of side branch vascular interlayer was lower.