Objective: To explore the value of SYNTAX revascularization index (SRI) on evaluating the long-term prognosis of coronary artery disease (CAD) patients implanted with biodegradable polymer drug-eluting stents (BP-DES) and define the best threshold of SRI for predicting all-cause mortality in these patients. Methods: Data used in this study derived from the I-LOVE-IT 2 trial (evaluate safety and effectiveness of the Tivoli DES and the Firebird DES for treatment of coronary). I-LOVE-IT 2 trial was a prospective, multicenter, randomized, assessor-blinded, non-inferiority study. A total of 1 829 patients implanted with BP-DES were divided into 3 groups, namely SRI=100% group (n=963), 50%≤SRI<100% group (n=527) and SRI<50% group (n=339). The primary endpoint was 48-month patient-oriented composite endpoint (PoCE), a composite of all-cause mortality, myocardial infarction(MI), stroke, and/or any revascularization. The secondary endpoints were components of PoCE and definite/probable stent thrombosis at 48 months. The receiver operating characteristic curve was used to investigate the best cut-off point of SRI for 48-month all-cause mortality. The Cox regression analysis was used to identify independent predictors of the all-cause death and PoCE at 48 months. Results: Incidence of PoCE at 48 months was significantly lower in SRI=100% group than patients with 50%≤SRI<100%(17.34% (167/963) vs. 22.20% (117/527), P<0.05) and SRI<50% (17.34% (167/963) vs. 24.78% (84/339), P<0.05). Comparing with SRI=100% group, the patients with 50%≤SRI<100% suffered higher rates of all MI (7.78% (41/527) vs. 4.26% (41/963), P<0.05) and target vessel MI (6.45% (34/527) vs. 4.26% (41/963), P<0.05); patients with SRI<50% had higher rates of all-cause mortality (5.90% (20/339) vs. 3.12% (30/963), P<0.05) and any revascularization (14.16% (48/339) vs. 3.12% (30/963), P<0.05). The receiver operating characteristic curve analysis showed that the SRI=65% was the best cut-off point to predict the all-cause mortality at 48 months (area under the curve was 0.58, sensitive was 0.47, specificity was 0.70). Meanwhile, SRI<65% was an independent predictor of 48-month all-cause mortality (HR=2.06, 95%CI 1.25-3.38) and PoCE (HR=1.34, 95%CI 1.09-1.66). Conclusions SRI serves as a good index for predicting long-term prognosis and SRI<65% is an independent predictor of 48-month PoCE and all-cause mortality for CAD patients with BP-DES implantation. Meanwhile, SRI≥65% might be a reasonable threshold of incomplete revascularization.