Objective: To compare the protection effects between side branch balloon submerged embedding technique and side branch guide wire protection technique on the side branch in the process of main branch stent implantation during PCI for true coronary bifurcations. Methods: A total of 44 patients with true coronary bifurcations were randomly divided into two groups: group A and group B. Twenty cases in group A were treated with side branch balloon submerged embedding technique and the other 24 patients in group B were treated with side branch guide wire protection technique. Several parameters were compared， including the damage rate of the ostium of the side branch， the severe damage rate of the ostium of the side branch， the loss rate of the side branch， guide wire exchange time， the X-ray exposure amount， contrast agent dosage， the rising rates of postoperative TNT-h， and the rate of postoperative ischemic chest pain. Results: There were no statistic differences in the damage rate of the ostium of the side branch， the loss rate of the side branch， and the rate of postoperative ischemic chest pain （all P>0.05）. The severe damage rate of the ostium of the side branch， guide wire exchange time， the X-ray exposure amount， contrast agent dosage， and the rising rate of postoperative TNT-h had statistical differences （all P<0.05）. The incidence of major cardiovascular events （MACE） after 8 to 12 months follow-up had no significant difference（P>0.05）. Conclusion: During PCI for true coronary bifurcations， the side branch balloon submerged embedding technique can reduce the severity of the ostium of the side branch damage， increase the successful rate of guide wire exchanging， shorten operation time， reduce X-ray exposure amount， contrast agent dosage and myocardial damage compared with the side branch guide wire protection technique after main branch stent implantation.